Allende in Chile, for example. Argentina, Brasil, Uruguay got support for their torture programs. Nicaragua brought Oli North to the surface, Grenada even got a full-blown invasion for having the audacity to be slightly left leaning.
Cuba also got its bay of pigs and several assassination attempts, but admittedly, Castro wasn't exactly elected - though the dictator he ousted was supported by the US.
No, because we usually don't find out until there is a leak or it is declassified. I had long conversation with a policy friend last weekend trying to figure out which countries the US didn't undermine at then highest level in the middle east. It started with Iran and Iraq, and ended up with hmmmm... how much of the Arab spring were we part of and how will it make things 10x worse again.