DF is correct. If you want to u/g on UA, you'll have to fly thru ORD -- 1.5 hours on 319 or 733 (or similar) in UA F really gets you a whole lot of nothing besides a comfy seat (if that is what makes you happy, then go for it). If you fly through PIT or PHL on US, or IAD on UA, you're gonna be on an RJ 95% of the time on the transborder segment. Not sure about CLT.

Looks like your choices suck, no matter what you do

However, FGII does make a good point about E+... but then again... ORD/IAD are your only choices here (YYZ IAD always CRJ on UA/AC except I remember a year or more ago the IAD YYZ/YOW/YUL routes on AC metal did actually have 319's).