That's a good question; one that not many people really want to know the answer to - because the predetermined conclusion that they have been taught to believe refuses to accept any facts to the contrary.
Zionism is a political segment of pseudo-Judaism that claims to represent all of the Jews. But this representation extends only as far as the benefits they exploit using the Jews as a shield to hide their true agenda. Just the fact that they're political should support this fact.
It was these Zionists who committed treason against Germany in 1917 when they suckered the United States into WW1 on the side of Britain in exchange for the rights to Palestine. They had gotten a foothold in the American government through Alexander Hamilton and the establishment of America's first Jewish controlled central banking system.
Political Judaism as practiced today originated in the 1700s (before it was called 'Zionism') when it was embraced by Meyer Amsel Rothschild. A quote attributed to him - "Give me control of the world's money supply and I care not who makes the laws" is highly debated and accepted as not coming from him. However, considering who he was and his goal to become the wealthiest family in the world follows this quote exactly. It is the working agenda for the Zionists and to disassociate the phrase away from him for the purpose of creating a distraction would easily fall in line with the sleight-of-hand practices the Zionists use as part of their daily protocol.
Woodrow Wilson was blackmailed into appointing Louis Brandies as the first Jewish judge on the Supreme Court. But the blackmail didn't end there - he was also manipulated to get America involved in WW1. When Germany was defeated in that war, the reparations against them were strongly influenced by the Zionists and thus as harsh as they could possibly make them. This weakened to the point that they were left vulnerable to being controlled by the Zionists, which they did for the next 14 years as they continued to destroy Germany from within and keep the German people starving, homeless and unemployed.
When Hitler became Chancellor, he took all of it away from the Zionists and set about restoring Germany - which he did in just 6 years. Being evicted from their positions of power and control infuriated the Zionists, and they declared war in retaliation, as well as initiate the most devastating hate campaign in history.
Roosevelt, who was of Jewish ancestry immediately threw his support for the Zionists - by then, a large percentage of Washington's movers and shakers were Jewish, and Roosevelt had strong Jewish support. He immediately set out to refuel hostilities between Poland and Germany that had been a source of conflict ever since the Versailles Treaty divided Germany and gave parts of it to Poland - especially the area that was known as the Polish corridor, which cut off Danzig and East Prussia from support and protection from Germany.
During this time, Roosevelt was acting the part of isolationism to real public support (and keep his job), while at the same time, spreading innuendos about the non-existent possibility of Hitler attacking America. He wanted into a war with Germany on behalf of the Zionists, and as much public support as he was able to get for his domestic policies, he couldn't broach the idea of getting involved in the growing European conflict. The first war that America was suckered into was still too fresh in their minds, and to suggest getting involved would have labeled him a liar in his campaign speeches where he promised he would never send "America's boys" to fight in another war on the other side of the world that was of no concern to Americans.
But his innuendos weren't finding their mark, so he had to devise another plan. This one would involve orchestrating an embargo against Japanese oil purchases, and then lead them to America with promises of being the only oil supplier they had to turn to. After laying a trail of breadcrumbs for them to follow, he slammed the door shut in their faces, knowing that the possibilities were excellent for them to retaliate with an attack.
Once they did, it created such a shockwave that he got the support he wanted to go to war with Germany.
But it wasn't just about supporting the Zionists. Roosevelt was also a failure in his public works programs that he created in an effort to pull the United States out of the Great Depression. One of the failed ideas he had was to take America off of the gold standard (1934). He took away the precious metal that gave America's currency its value and replaced it with fiat money - totally worthless.Instead of rescinding the act, he literally robbed the American people by outlawing personal possession of gold.
Unfortunately, the world economy is based on the United States dollar, and by rendering the dollar worthless in America, its value plunged everywhere else, also. This is why he illegally gave so much support for the war to as many other countries as he did. He had to try to appease everyone until he could get involved in the and smooth things over.
EDIT: It's ironically funny how people hate the Nazis because, for one reason, it indoctrinated people to prevent them from thinking for themselves. And yet, this is exactly what forcing support for the Holocaust does. There is nothing in acceptable documented history that supports anything anti-Holocaust nor anti-Jewish. The documentation that does exist is condemned as hate speech and is immediately discarded. And the worst part is people don't even realize that they're being led by the nose. They've been taught what to believe and going against this belief creates a mental turmoil when actual documented facts are introduced - it's called "cognisant dissonance". They would rather go on believing the lies they've been fed. Thus the well-known saying:
"People don't really want to know the truth, just want reassurance that what they believe is the truth."