Question

In world war 1 how did America decided to intervene ?

Answer 1

Well, what really kicked America to intervene in WW1 was Germany declaring unrestricted submarine warfare in 1915 ish. Until then America was neutral though partially supporting the Allies with their Cash and Carry policy which due to the UK's dominion over the sea, basically meant they and their allies were the only people who could get the cash to America and carry it back.

The unrestricted submarine warfare and the death of american sailors due to it kicked America on the UK's side against Germany.