I have flown across Canada for decades without talking to ATC or
filing a flight plan... I have stopped doing that since 9/11 - period!

It doesn't matter whether you are just crossing over the Windsor VOR
for a few miles, or flying hundreds of miles into Canada.. It is a
violation of International Law to do so without a flight plan, and I
can guarantee you that the Homeland Security folks will be more than
happy to 'fold, spindle, and mutilate', and then go get their pats on
the back for "protecting" the country...

Now, avoiding that is stone simple... File a flight plan... OTOH, if
you forget and realize you are going to enter Canadian airspace (or
exit) simply call ATC and ask for Flight Following... That generates a
squawk code, you are in contact with ATC, and while it doesn't meet the
letter of the law, it demonstrates that you are a team player, not a
terrorist...

denny