None of them ever really turned on us, though sometimes we made bad bets like on South Vietnam, which pretty much only existed because we said it did. The people were pretty sympathetic to the communists on either side of the war.

The closest one came to doing so was Saddam Hussein, who enjoyed American support in his invasion of Iran in 1980, and later decided to invade Kuwait to aid their oil to his own and help recoup the losses experienced against Iran, which had devastated Iraq's treasury and people. Apparently US ambassador April Glaspie had given him reason to believe that the United States would support him in this venture, too, but instead we led a coalition of 34 countries against his own.

We funded fundamentalist Islamists in Afghanistan against the Soviet invasion but also Afghanistan's socialist government. A coup by a tiny group of Afghan communists overthrew the king in 1978 and in 1980 the Soviets invaded and took more-or-less direct control. The leftward swing of the pendulum here was pretty temporary and only triggered a massive tribal and religious insurgency that we gave money to because fuck the Soviets. They weren't terrorists then and they didn't really turn on us; it's more accurate to say we thought their aims would remain squarely in Afghanistan and didn't figure that there would be groups within the groups we funded with aims to broadcast their brand of fanaticism on an international scale. We figured incorrectly. I believe the exact quote afterward from Director of Central Intelligence Stansfield Turner was, "No one gives a damn about Afghanistan."

Another instance of us overthrowing a government under fears of communist sympathy that ended up backfiring was in Iran, where the Allies removed the dynastic despot Reza Shah Pahlavi for flirting with the Nazis. Iranians tried to restore their old constitution from the early 1900s, the one the shah had summarily ignored, and resurrect their parliament. They voted in a modernist named Muhammad Mosaddeq who pledged to recover total control of the country's oil reserves, and canceled Iran's contract with British Petroleum and announced he was nationalizing the Iranian oil industry.

Nice try, nerd.

The CIA kicked out the "madman Mosaddeq" (as our secretary of state, John Foster Dulles, called him) in 1953 and put Reza Shah Pahlavi's son, Reza Shah Pahlavi, on the throne, who signed a treaty with the US, giving an international oil consortium of oil corporations the job of managing Iran's oil. This is also why Iran and the Muslim world hates us, by the way; before this, they'd loved America for Woodrow Wilson's 14 Point Plan following World War I that seemed like a powerful bulwark against more European intervention in their affairs and led them to believe they had a friend in the United States. But pretty consistent meddling in affairs and propping up unpopular governments to get more oil just made them think we were no better than the Europeans. I can't really say they're wrong.