How Did The U.s.a. Enter World War 2?

It was under political pressure from the allies of Europe, particularly england, and finally goaded into action by the Japanese when they attacked pearl harbor- there's a reason they got nuked.

but probably one of the biggest reasons they entered world war two was the financial gain- the US, at that time, was under the incredible strain of the great depression. Entering the war gave them the chance to modernize the entire country essentially overnight- it allowed them to borrow money from europe so that they could mobilize the industries and develop new armaments and production capabilities, and this mobilization has only shifted, it has never really stopped- America, as a nation, still has one of the highest potential outputs of industrial product of any country.

the economic impact of this means that because america entered world war two, it became a world power: It had the means and the ability to produce anything, it had the very best of every type of technology (after the war, when it had imported German scientists), and on top of this, it still had the production capabilities it had created- essentially from nothing- during the beginning of the war.  The GI bill that the soldiers got meant that it had a college-educated workforce after that, which is the beginning of any nations economic climb- look at Korea, for instance, or Vietnam, or china, or India, or Singapore, or any nation.

world war 2 was probably one of the smartest moves by American leaders, ever. They had two distinct bad guys, a propaganda- hungry population, free foreign money, a chance to earn money on their own because of all of this, and all the moral justification you could hope for, entering a war. There was no cry of "they're people too", there were only cries of "those bastards!"

There are many more sides to it than this, and I'm simplifying a bit. But I think it gives a good overall picture of the biggest influences to go to war.

The U.S. Entered the war after Japan bombed Pearl Harbor.