There's a long list of countries where the US mounted prolonged campaigns to interfere and influence democratic elections as well as intervened militarily in Central and South America - perhaps Chile and the assassination of Salvador Allende provide one of the best examples of US/CIA intervention along side El Salvador and Guatemala. (Iran is also a great example of US/CIA intervention).

Here's a quote from Wikipedia on US involvement in Chile

According to the 1975 Church Commission Report, covert United States involvement in Chile in the decade between 1963 and 1973 was extensive and continuous. The CIA spent $8 million in the three years between 1970 and the military coup in September 1973,[9] with over $3 million in 1972 alone. Covert American activity was present in almost every major election in Chile in the decade between 1963 and 1973, but its actual effect on electoral outcomes is not altogether clear. Chile, more than any of its South American neighbours, had an extensive democratic tradition dating back to the early 1930s, and even before. Because of this, it is difficult to gauge how successful CIA tactics were in swaying voters.

They may not have convincingly swayed voters but they certainly enabled the coup d'etat that followed Allende's election.

Know your history America.

Great video by the way, i especially enjoyed the slow voice modulations in case anyone missed it ;)