No. You have the sequence of events quite wrong. The US started supplying the USSR for cash in mid-41, they joined Lend-Lease around October, Germany declared war in December 1941, partly of course because the US was supporting the UK and the USSR.
Incidentally the decision to support the UK was by no means obvious. The traditional ally of the US in Europe is France, not the UK (War of Independence, Napoleonic Wars, and in 1917 the US came to the aid of France, not Britain.) Once France had surrendered and done a deal with Hitler, the US had no particular reason to support a hopeless war. The decision was to a degree on ethical grounds - Hitler’s Germany was a wicked state run by wicked people.
No, the point I’m making is this, since it obviously needs hammering:
USSR - cruel dictatorship, but with an official philosophy which was benign, preaching equality of the whole human race and looking forward to an end to conflict. Some Russians wrote after the denunciation of Stalin of how they fought in WW2 because they knew Stalin’s government was evil but they hoped their children would live to see true communism.
Germany - cruel dictatorship with a cruel and evil official philosophy of German supremacy and the inferiority of most of the rest of the world.
US business didn’t care about the distinction, but FDR saw it very clearly.
2016 US election:
Democrats - deeply flawed candidate, but a party whose official philosophy is benign, being based in equality.
Republicans - deeply flawed candidate whose views are those of large numbers of his party, many of whom believe in the superiority of white men over everybody else, and in the inferiority of the rest of the world, and who want increased inequality.
I’m not doing a Godwin and saying a vote for Trump is like voting for Hitler, I am just saying that there are uncomfortable parallels, and that most people think FDR made the right call. He could have done a deal with Hitler, after all.