if you go to flighstats.com they will give you historical performance data for that flight. Delta also flies DCA-JFK so you have additional option if AA goes bad. or you can take the shuttle to LGA

It may be more wasteful (time-wise) to build in a two-hour cushion vs. a 35 minute connection time if the flight is only 10% of the time. Depends on how costly a delay/reschedule is.

I take this flight for european connections and haven't had trouble, but have presumed AA would protect me (unless it's weather-related) if something goes wrong on another flight on another airline.