[DanielBMarkham]

It could. Also pigs could learn aviation. It is unlikely for either to happen, however.

The U.S. has a built-in coup mechanism: the president effectively serves at the convenience of Congress. While he/she is an elected official and in a different branch of government, the constitution was pretty clear on who runs the show. The House and Senate can, at any time, remove the president from office.

It'd be a helluva thing to do, but military coups are fairly spectacular also. On any given day that both houses were in session, given a hated enough president, you could probably do the entire thing on a voice vote in an hour or so. At that point the military and police authorities would be responsible for removing the president and swearing in the new one.

You might be able to spin out some scenarios for a U.S. coup d'etat, but there is a very long line of tradition in the states that the military serves the civilian authority. I think most command-level officers are fairly well indoctrinated in avoiding that scenario at all costs.