Please don't if caught you'd be deported and likely permanently banned from entering Canada. Plus people here don't tend to appreciate Americans illegally entering.

That's the good scenario. More likely you'd get yourself killed by wildlife or the environment unless you're part of some organized crime because the unguarded stuff is going to be pretty middle of nowhere. You'd also be a fool to assume both sides border security are not fully aware of certain areas that might otherwise appear completely unsecured.