If the U.S. supports democracy, then why did it overthrow democratic governments?

I am referring to - the CIA supporting the coup in Chile to overthrow Salvador Allende who was democratically elected - the coup in Iran against democratically elected Muhammad Mossedegh - Overthrowing Jacabo Orenz in Guatemala because he tried to get land reform - Overthrowing Goulart in Brazil because he was a leftist - Lumumba in the Congo