Without data sheet on Armstrong AC unit, it's hard to tell if load will exceed capacity of Honda Eu2000 generator, but odds are huge it will..
Most of 11K to 15K BTU AC units have both "startup" and steady load ratings, and higher startup load in amps is necessary to get compressor started. It is usually in range of 20 to 25 amps... A 20 Amp load at 110V is approx 2200 watts, and most trailers siphon off some of the 110V power in the univolt/transformer for 12V
and battery charging, leaving less than you started with available for AC.. Honda (or similar) 2KW generators are designed to put out peak of 2000 watts for brief periods, but no more, and will trip at 2100 or 2200 required. They're really happ and efficient putting out 1500
or 1600 watts. There are several threads on website of happy owners who buy 2 of Honda EU2000's, and connect them in parallel, rather than use big 3500 watt generator which very few of us can muscle in or out of a van or Suburban.. (Most weigh over 135 pounds, plus gasoline)...
Lots of other threads warn of attempting to run AC compressors on insufficient wattage and damaging unit or destroying it... This can happen as well by stringing lightweight extension cord from house to trailer in back or side yard... (I've melted a pair of orange outdoor cords doing this when younger and less educated.. say in 1980's..)