Coleman Roof AC Help.. Sat upside down, now won't work!

The AC should run on a 15A circuit as long as that's all that's on at the time and had adequate voltage. As far as the converter overloading anything, probably not. The breaker that powers the converter is separate from the 20A one that feeds that AC. If the converter had a problem creating an overload, it would likely trip it's own breaker. If there was low voltage, the AC would start and run, unless line voltage was VERY low, but would eventually draw excess current and probably trip it's own breaker.