Here are my 2 cents:
1.I think that a war could only be won by having air supremacy over sea and land.
2. Maybe if the Me262 would have been in service earlier, it would have cleared the skies over nazi occupied Europe and in Russia, allowing the bombers to hammer into oblivion any resistance.
3.The u-boats could have roamed with more freedom and if the type xxi was introduced earlier maybe they would have blocked the Atlantic.
However those said above would also force a massive involvement from USA, and i think the first nuke would have been dropped on Berlin