Was hitler's power in europe was seriously checked when the united states entered the war.

This is more of an opinion question, but if you have an american teacher then you might want to say yes. After japan attacked the us in dec7, hitler soon delared war on america, this was during the time they had reached the gates of moskow. and have been making advances into north africa. They soon got stopped however by the british in al alemain. it wasn't untill in the later year of 1942 did they start opration torch, so I would say no.

I hope this helps
M=30g