I was wondering this. In the same way that the USA has supported, sometimes armed, sometimes covertly, sometimes not, right wing governments in places like South America, are there any leftist, or more specifically socialist regimes in he world that the US has propped up and armed in a similarly Machiavellian way? I understand that this sort of approach was more of a CIA thing, and so was historically an anti-communist thing. But I was curious if the US ever saw fit to arm and aid left wing regimes or fighters as intimately as they did (radically)right wing ones.
EDIT: Yugoslavia is a good example, as well as /u/gmoney8869's mention of flirting with Pol Pot. These regimes I think saw themselves as properly instruments of that whole socialist dialectical trajectory. In other words I think both of these regimes conducted themselves as though they were helping to one day achieve communism. Examples I am not so much looking for would be social democracy regimes that more often than not emerged from the Marshall plan and concerned itself with supplementing a market economy with social services and welfare, but with no revolutionary aspirations.
EDIT 2:
I forgot to ask if there were not just regimes but fighters, maybe militant stateless factions, guerrilla cells, or even more above ground movements that one would consider pretty "red" yet may have received aid, money, training, weapons, intel, that kind of thing from the US.
In the early days of the Republic, the U.S. government supported a number of regimes that would more than likely be considered "left of center" in later years. Under President Adams, the U.S. Navy covertly supplied the young Republic of Haiti; U.S. forces fought alongside Haitian soldiers in several small firefights. A few years later, the U.S. government offered quiet support to a number of revolutionary regimes across Spain's American colonies.
The progressive government of Benito Juarez received covert U.S. funding against the brief Imperial Mexico of Maximilian I throughout the Civil War, and U.S. troops participated in some skirmishes against Maximilian after the war.
In the runup to the Spanish-American War, the plight of the heroic Cubans was trumpeted in every major American newspaper - but after the war, it became plain to a public that didn't know it that the majority of the Cuban freedom fighters were black former slaves who'd been fighting to gain control of their lives from Spanish overseers.
(This is obviously not an exhaustive list.)
I imagine that what you're looking for, though, is a Cold War example. The showcase example there is Yugoslavia. In 1948, Yugoslavia's dictator (and WW2 partisan hero) Josip Tito broke with Stalin, and promptly applied for Marshall Plan aid. In order to prop up a socialist government without connections to the Warsaw Pact, Truman and his successors provided economic aid to and traded with Yugoslavia.
Throughout the 1950s, Yugoslavia received nearly $2 billion in U.S. economic and military aid, equal to about 1 percent of its annual GDP. (Another example that might strike a chord with Redditors of a certain age: low tariffs allowed the import of cheap Yugo cars in the 1980s.) Support continued on a smaller scale up until the collapse of Yugoslavia at the Cold War's end.
Secretary of State Henry Kissinger discusses the Khmer Rouge regime with Thailand's Foreign Minister Chatichai, November 26, 1975:
Kissinger: "You should also tell the Cambodians that we will be friends with them. They are murderous thugs, but we won't let that stand in our way. We are prepared to improve relations with them."
Kenton Clymer, The United States and Cambodia, 1969-2000: A Troubled Relationship (New York and London: Routledge, 2004)
Former US National Security Adviser, Zbigniew Brzezinski, on China and the Khmer Rouge, 1979:
“I encouraged the Chinese to support Pol Pot. Pol Pot was an abomination. We could never support him, but China could.” According to Brzezinski, the USA “winked, semi-publicly” at Chinese and Thai aid to the Khmer Rouge.
Elizabeth Becker, When the War Was Over, New York, Touchstone, 1986, p. 440