When Mary Winchester brings Asa Fox home in 1980, there is a second generation Chevrolet S-10 extended cab pickup in the drive. As the S-10 was not produced until the 1982 model year (late 1981), one could not exist, let alone a second generation model (1994 to 2004).
There's no way Sam and Dean could go to Canada, or any other country for that matter. They would immediately be detained and jailed upon trying to re-enter the United States. 1-They would have to show their actual IDs to get back in, and that would pop them up as people who supposedly died, more than once, after being on the FBI's most wanted list. 2-Their car would be inspected, and the authorities would find a trunk full of not only weapons, but fake IDs.
Sam and Dean insist that Jodi Mills let them come with her to the funeral of Asa. They end up driving her in their car five hours to Canada. At the end, the boys leave for breakfast with their mother and then back home. They left Jodi behind, and she now has no way to get back home 5 hours away.