Of course we supported Stalin and Mao, they were allies against Hitler, and we needed their help. I hope you're not suggesting we shouldn't have helped our allies in WW2?Are you actually that ignorant? The American Left - Communists, Socialists, New Dealers - were avid ideological supporters of the Soviets and later Mao. And the history is clear that there was quite a bit of spying done by Americans for the Soviets. Do some research on "Communist Party USA."
As far as material support goes, Americans, outside of the labor unions and academia, were generally more focused on doing business than following political distinctions. Consider that Henry Ford built a huge auto plant in Nizhni Novgorod, a deal worth a staggering forty million dollars - 1930s millions paid for in gold at the height of the Depression. No other firm in the United States or even in the world conducted as much business with Joseph Stalin than the Ford Motor Company between 1929 and 1936. But, then again, Ford and the Nazis were mutual admirers, so who knows how the politics played out in the background.
In 1941, before the United States entered the war, President Roosevelt sent $11.3 billion worth of U.S. military aid to the Soviets under the Lend-Lease program. And he did the same kind of deal with China, when the Communists and the rest of the factions were somewhat united against common enemies.
That there was little material support of Mao initially by Americans is more a case that there was no clear understanding of what was going on in the Chinese civil war and who the players might become. A bit more on the complications can be found here -
Subsequently, China was isolationist and there was little more than a lot of hot air and propaganda by lefties that, in fact, knew nothing about what was actually happening in China, including the joys of the Great Leap Forward and the Cultural Revolution. So, technically, you are right in that no arms or material support went from the American left to Mao, just propaganda support by lefties, who seem to absolutely love all sorts of mass murderers.
Lots of complications in the history and it takes a lot of reading to get understanding. I can suggest reading some books on what life was like then and who was sleeping with whom and the consequences that resulted. The first book studies the Left's historical adoption of all the wrong choices for liberty and democracy, the rest are specific to the Stalinist period and last one with a definitive history of Mao.
United in Hate: The Left's Romance with Tyranny and Terror
by Jamie Glazov
Koba the Dread: Laughter and the Twenty Million
by Martin Amis
The Forsaken: An American Tragedy in Stalin's Russia
by Tim Tzouliadis
Mao: The Unknown Story
by Jung Chang and Jon Halliday
And it was the right wing helping the Nazis, google Prescott Bush.
The recent history, the last 50 years, is of the right in America funding and protecting monstrous dictatorships, not the left.