U.S. in World War 1

What year did the U.S. enter WW1?

What country was a major reason why the U.S. Entered the war?

What was the name of one of the British ships that Germany sank?

What was the name of the telegram that Germany sent to Mexico?

Who did the U.S. Declare war on when they entered the war?

Which was not a reason the U.S. entered WW1?