If I read it right, your flying from DC to JFK and then on to Argentina. There are no immigration formalities on leaving the United States. No passport control. You are simply connecting and if you're connecting on the same airline or in the same terminal. you simply exit the first plane, look up your gate on the monitor and go to the gate (presuming you get your boarding pass when checking in at DC)....if you're changng terminals you go outside, take the air train to the new terminal and again if you already have your boarding pass, just go through security to the gate of the departing plane. If it's a legal connection, you don't need a whole lot of time but as always that is dependent on ATC problems, weather problems and whatever.

Departing the US on an international flight doesn't really cause many problems. The only hang up is the usual security if you are changing terminals.

The main issue will be flight delays and baggage transfers. My bet is that you will not make the connection. I bet you don't make the connection. I would do my best to get an earlier first flight. Really no one should be selling that ticket nor telling you rhat you will make it. Just my opinion.

Everyday, the vast majority of passengers in the US make 55-minute connections. It's clearly not absolute, but saying that you will not make it is pretty ridiculous. If you're connecting on same airline without having to reclear security, I'll bet against the previous poster.

These are AA flights, it is a legal connection, and the OP has an excellent chance of making the flight.

The flight from Washington is on-time 95% of the time. Even if the flight is slightly late (though not if it's hours late), AA will hold the departure for B.A. to let the passengers and their luggage connect.