The CIA installed the Shah of Iran after the elected government started talking about nationalizing the oil industry.
I feel the need to point out that nationalizing the oil industry wasn't the catalyst for CIA involvement (just the catalyst for British involvement); we actually initially refused the British on anti-colonial grounds, for similar reasons as to why we got involved in the Suez Canal Crisis against Britain, France, and Israel. The US intelligence services didn't get involved with the overthrow of Mossadegh until (mostly unfounded) fears that the Tudeh Party would replace him were stoked.