I don't think it was a matter of choice for many. The world as a whole did not enter, the individual countries that did however, did so in accordance with their own interests or beliefs.
No
1934
Yes
2011
yes it was vital 4 the US 2 enter World War 2 because we needed their help 2 win the war. It turns out tht because of them we won the war.
At the start of the War they were always in
World War 2
They entered the war in 3333
cause they wanted to! =)
1941
They were allies with Germany.
1991