What actually cause them to join the war was the attack on Pearl Harbor
The US and the Allies won the war and the US gained control of the Philippines, causing it to become a world power.
The nuclear weapons that the super power countries had caused international tensions after World War 2. This caused the Cold war between the US and Russia.
Gremany
do you mean what caused us entry into world war one? if so then the sinking of the USS Lusitania by German u-boats was what caused American entry into the war
US, Australia, New Zealand, Philippines, Thailand, S. Korea, S. Vietnam against North Vietnam and VC.
the sinking of the ship lusitania:)
US wanted to trade with the other countries causing them to get involved in the war
Pearl harbor.
World War II
it caused the economy to go down
Europe needed help and weapons