Why did the United States and the USSR fight together as allies in 1941?

and Did the United States and the USSR ever fully trust one another? Explain plz

Because Hitler went back on his word, and I would assume not.

Explanation:

Hitler attacked Russia forcing Russia to enter WWII against them. This put the US and USSR on the same side. I don't think they fully trusted each other past temporary allies because of the vastly different ideologies they had. They were polar opposites.

the answer should be:

their party has more members.

if i am right, give me a 5 star rating!

when world war i broke out across europe in 1914, president woodrow wilson proclaimed the united states would remain neutral, and many americans supported this policy of nonintervention. however, public opinion about neutrality started to change after the sinking of the british ocean liner lusitania by a german u-boat in 1915; almost 2,000 people perished, including 128 americans. along with news of the zimmerman telegram threatening an alliance between germany and mexico, wilson asked congress for a declaration of war against germany. the u.s. officially entered the conflict on april 6, 1917.