From what I know, having to be at the airport 2 hours on a normal (non holiday) flight in country is just barely enough time when there are mitigating circumstances. (Then, add need to use restroom, or buy water or food...)

I would say at least 4 hours on an international flight...but would count on 6 personally. Now, IF you arrive and do not have to leave the checked-in area, you wouldn't need as much time. This is assuming you don't have to go back through baggage check in since the airlines should be swapping your luggage and you've already entered the secure area and haven't left it. THEN I would say 4 hours might be enough.