2Hondadude...a used Cobalt is bad?...okay...i'll file that info (tapping my weenoggin')
My Eagle Vision TSI was a 3.5l engine, and yes, a bit of a fuel pig, but i got used to slidin' my 5'9", auburn-haired self into that roomy frontseat...had power thisnthat...includin' compass and outside temp...i really dunnawant a "collegecar", if ya know what i mean...4cyl...yikes!...isn't that like drivining a sewing machine with 4 wheels?....(musin')...mmmm...luuuuuv those powerseats too...(like Homer luvs donuts)

Four cylinder engines have come a long way, trust me. There are at least four of us on this forum drive a non-turbo 4cyl car that stickers close to $40k, and nobody has complained about the engine yet.

Vibe could be a good choice. It came a bit better equipped, if I recall correctly, than its Matrix counterpart. GM price with Toyota reliability. Kind of anemic power though, compared to its more modern counterparts, as the Corolla platform is very (VERY) long in the tooth.
Also agree on the Cobalt, as in avoid the ex-rentals / demos. They will have had a very rough life.
Do you really have no access to anything other than domestic dealers? Your options would expand greatly. Someone posted that Hyundai was offering 0% financing over
72 months on 07 Sonatas. Thats just outstanding. Another forum goer recently bought a 07 Sonata GL Manual for a shade under $20k, plus tax. Financed at 0%, its like not paying any tax (guessing...haven't run the numbers). Hyundai has made great strides, and I imagine the 4 cylinder offering is at least as good as the domestic ones. Worth a shot if you have dealer support in a nearby town.
As far as used options, for $20k there are many. Wouldn't spend $20k on most used cars though if you're just looking for basic transpo.
EDIT: Vibe also has available AWD...could be worth it for those Northern Ontario winters (I grew up in Sudbury). Saps even more of what precious little power the car has, though.