The US was neutral and did business with both allied and axis powers at that point. We nevertheless tipped the scales strongly in favor of the allies with the lend lease act, for example. And the historical record is pretty clear that from the beginning of the war, Roosevelt was itching for a reason to jump in on the allied side. Your anti-American historical revisionism is contrary to the facts.

The idea that the US should stop doing business with China is ridiculous. As a major nuclear power with an economy that within in a decade or two could surpass ours in total output, America is in no position to do anything about China's internal affairs. Ending trade with China would cause extreme economic damage and internal unrest in the United States. It would be a phenomenally stupid sword for America to fall on.

You're right in general though. America's main interest after the security of ourselves and our allies is open and peaceful commerce between nations.