What was the United States role in Europe and the Pacific Theatre during WWII?

The U.S. was pretty much in control of the Pacific Theatre, they fought many naval and air battles in the surrounding seas also. One of the main reasons for participation in the Pacific was to re-liberate the Phillipines (a U.S. territory at the time). In Europe and Africa the French, English, and Russians were getting their butts kicked really badly and called on the U.S. for help. Also America did not like the use of unrestricted submarine warfare (as the Germans used) but ended up using the same tactic themselves.