A Q on US Ships
 

I note that there are US warships in the game (I've yet to really get in to it) and was wondering if they are just there for show ?

You occasionally see them moving around in task forces. Depending on the mod they also engage in some of the historical battles with the Japanese on select dates. Savo Island, Cape Esperance, Guadalcanal, etc.

try the midway battle single mission its fantastic, JIN vs USN mashup!
planes, heavy gunnery and you stuck in the middle firing at the fattest battleships ;)