To be fair, I don;t think there is any plausible scenario where they could have made the right decisions and changed the outcome... :)

I think you're absolutley right. Japan's entire strategy and composition was based around the quick strike; the one punch knockout. They were counting on a decisive blow forcing the US to sue for peace. Once it became a war of attrition, it was all but over for Japan.

I read a stat once that the US built more tonnage from jan 1, 1943, until June '43 than Japan built from 1937 - 1945 combined. And we'd not really even hit our stride yet.

The Arsenal of Democracy was indeed a well-deserved title.

Well they didn't really have a bad fleet, but more bad doctrine
nothing wrong with their battleship orientated fleet, most navies were like that at the time

surprisingly Japan didn't (or was unwilling to) understand the importance of merchants and convoys

they only created a department for escorting merchants in 43, and only 2nd rate crews were for escort duty

before 43 they used fleet destroyers with crew trained for fleet engagements for escorts.

And the US couldn't have lost, with all those carriers and battleships built during the war

This guy would beg to differ with you, vis a vis CAS; my only addition would be that the Soviets & Germans both had the need to develop CAS a lot sooner than did the US, as we weren't even engaged in large-scale land combat until Africa in 42, where the Russians and Germans had been throwing a lot of lead at each other for a couple of years already.

Exactly.

The resources at hand, manufacturing capabilities, the skill and temperament of the troops, the vision of it's leaders, what it takes to transport troops and materiel out to the battlefield, it all has an effect on the type and quality of the weapons an Army or Navy fields and therefore what combat tactics are employed.

If we'd have fielded tanks similar to the German heavies it would have meant we'd have fielded far less tanks than we did. Even if you apply our manufacturing capabilities they'd still have to be transported thousands of miles across the ocean. That means less of them, and less of the other things that could have occupied the cargo space, that reaches the far off battlefields of Europe and the Pacific. It also means we advance slower. The Sherman's speed and reliability go a long way to trump armor thickness and firepower (and optics).

In short Tigers and Panthers may have been the best choice for the Germans but not necessarily for us.

As for troop comparisons, I don't really think there is such a thing as "the best" troops.

I'd put our top divisions up against any ones, friend or foe. For example Fraus boyfriend Dicky Winters took a half dozen men up against an entire Infantry company defending an artillery battery and kicked their butts. Who fields the better Soldier again?

The true picture is however that there was no shortage of guts or fighting ability on any side during the war. American, German, British, Aussie, Soviet, Chinese, Japanese and the rest, even the Italians, all have distinguished themselves on the battlefield.

When men are sufficiently trained, motivated, and led they can achieve great things. Nationality is immaterial except in the degree a nation can supply those things to their troops when they need them.

Half, a third, quarter, even a 5th. It still is an enormous contribution that contributed much to the eventual Soviet success. After all they didn't win by very much. A mere 5th less of something might have made the difference at the critical moment.

I did some research and it seems like General Quesada had the right idea, thanks for bringing him to my attention. However, his ideas did not win out. The US never really adopted CAS as a combat doctrine during the war. Unescorted daylight strategic bombing with massive losses were the rule at the time. Such results would suggest that something about the military system itself needed to be changed. Even then, it took almost 40 years for the US military to concede that the German military model for CAS was superior by all but completely adopting it, along with virtually every other aspect of it. Something is rotten in the state of Denmark and it isn't the Germans.

Didn't the Marines do a fair amount of CAS development in the Pacific?

CAS development? Are you serious? What the Marines developed during the Pacific war was a way of throwing men and machines at worthless targets with no justifiable effect. The only thing seperating us from the Army in that conflict is some really good PR.

And since I shoved an oar into the conversation already, I guess I oughta contribute something.

Light Infantry: USMC. Pound for pound, the deadliest light-fighters of the war, facing a relentless, persistent foe that yielded nothing before death.
Line Infantry: Imperial Japanese Army. The soldiers of Dai Nippon Teikoku - Ruthless, entirely committed to every fight, complete unwillingness to stand down or surrender. "Duty is heavy; death, lighter than a feather."
Armor: Germany. If the argument is quality, then the Panther Ausf. G wins, hands down. Good ground speed, ground pressure, excellent armor protection from most everything in the Allied arsenal, and deadly main armament created an epic combination of mobility, firepower, and protection.
Artillery: USSR. What the Germans did with six rockets (Nebelwerfer - the "Screaming Meemies"), the Sovs did with truckloads of 'em (Katyusha - "Stalin's Organ"). Modern Rocket artillery says, "Spasiba!" And we don't even need to begin to look at tube artillery - the Sovs practically wrote the book on that.
Fighter Aircraft: US. Sucked at the beginning of the war - who thought it was a good idea to fly a Buffalo? - but by the war's end, the quality and design of US fighter aircraft surpassed everyone. Arguably the best aircraft of the war in the North American P-51; the premier naval aircraft in the F6F; the USMC multirole fighter-bomber in the F4U - which continued to serve and fought in Korea, even as jets emerged onto the scene; the tenacious and durable fighter-turned-mud-mover in the P-47. These were the same designers who created the A-1 Skyraider - first flown in 45 and served until the 70's. Others may be faster, or prettier (I'm looking at you, FW-190D9), but I'll go with the American fighters.
Tactical Air Support: USSR. Developed because they had to, or die trying. Nobody was great at air-ground liaising in WW2, except perhaps the USMC at the end of the war in the Pacific, but the Sovs did the best job of a bad lot, developing their tactics - pardon the pun - on the fly, even as the Wehrmacht was attacking the airfields the pilots just took off from.
Strategic Bombing: USAAF (43-45). While strategic bombing was a flawed concept (Guilio Douhet, Billy Mitchell) based on postwar review of the stalemate in the trenches of the First World War, the USAAF proved that it could still serve a role in diverting assets away from other wartime industries; most notably, by creating a fuel crisis in Germany that made mechanized activity next to impossible, and diverting aircraft away from other activities - first to intercept the bombers, then to escort other interceptors. The equipment was right, the men were right, even though the concept of bombing a nation's cities to encourage its surrender was fundamentally flawed, as had already been proven by the Brits during the Blitz. Nobody else could match the USAAF in heavy bomber, precision-bombing output.
Submarines: USN. With only 52 boats lost, the US Navy's submarines did exactly what the Kriegsmarine wanted the unterseeboote to do - completely and totally isolate an island economy. And in the case of the USN, those boats were responsible for at least half of the IJN's maritime losses, while comprising less than two percent of the USN manpower. there is simply no equivalent efficiency in any other service of any other nation. Other boats may have been better built, but none match the USN's submarine RoI.
Surface Fleet: USN. By dint of sheer tonnage, the USN wins. The US fielded almost as many fleet carriers as Japan had in total carriers; add the jeep and escort carriers into the mix, and it's no contest. Then there's the destroyers - the big kids and the little DEs. Again, numbers and training far surpass anyone else at the time. True, the Japanese and the Germans fielded impressive BBs in Yamato, Musashi, Bismarck, Tirpitz, and others, but Wisconsin, Iowa, Missouri, and New Jersey are also wartime developments, and those would have been protected by swarms of carrier aircraft. Even if they weren't, I point interested observers to the fate of Sprague's Taffy 3 - a bunch of destroyers taking on battleships and cruisers, and turning them back. Training, audacity, and numbers - I like that in a surface fleet.

Logistics, (broken down by Staff responsibilities):
S1 (personnel & administration): UK. Civilians beyond military service age serving as Air Wardens, and in air defence capacities. Women in service, in more diverse roles, largely due to necessity (smallish population); nonetheless, a good example of using maximum available personnel resources. (I know the Sovs fielded women, too, some by accident, some by design; imo the English did it better.)
S2 (intel): UK. Preserved internal security fairly well; developed the answer to Enigma with the assistance of the Polish. The US wouldn't even turn the lights off on the coast during Paukenschlag.
S3 (operations): UK. Managed the defence of the Home Isle with not much in the way of supply, exhausted pilots, battle-weary aircraft, and air defence artillery partly comprised of reservists, all against a first-rate air force (Luftwaffe), while simultaneously working to keep convoys protected and trying to hold on in Africa and the Far East.
S4 (logistics): US. Two wars in opposite directions, both of which required moving a lot of stuff across land and a lot of water. US infantry might have trained with wooden dummy rifles in 41 and 42, but they didn't have to worry about having to field strip the dead for a real one when they hit the combat zone; rarely did the poor doggie wonder who's airplane that was overhead.
S5 (plans): US. Specifically, all of the planning required for Operation Overlord and the literally dozens of supporting plans that all had to work for the invasion to succeed.

The only thing I would add is that the XVIII Fighter Command began releasing their Thunderbolts and Mustangs to fighter sweeps in mid-to-late 44, as the Luftwaffe began its terminal fade; such sweeps included low-level attacks on targets of opportunity. However, they began to see increases in pilot losses due to the ever-present threat of flak - down to guys on the ground shooting rifles into the strafing aircraft - as well as the inherent hazards of flying fighter aircraft at single-digit altitudes and high rates of speed; they slapped a moratorium on low-level antics in, iirc, March of 45, to last until the end of the war.

I thought the Marines had begun the practice of using FAC's as early as Guadalcanal. I guess I was mistaken.

But don't you think "throwing men and machines at worthless targets of no justifiable effect" is kind of harsh for men who managed to win their war against a tenacious and committed enemy with less casualties than we suffered in a single Civil war battle?

Jap as line infantry?

They were terrorized when they faced real armies that actually had artillery that didn't use 3-4 guys on foot as the prime mover. They were utterly shattered by the Soviets before the war started. They won an excellent victory in Malaya, but everywhere else? When did they win in a real fight?

"Fighting spirit" is meaningless, or they'd have won the war.