The area is sparsely populated compared to the US. Most drivers going from Port Huron to Buffalo would use the 402, 403, & 401 superhighway combination to make the trip. Those roads are heavily trafficked. If you chose Route 3 which is the more scenic two lane route the amount of traffic is probably much less. The terrain is relatively flat and the locals who know the roads fairly well are more likely to take a chance that they will not meet something coming the other way. If they see a USA license plate as opposed to an Ontario one they take it for granted that you are unfamiliar with the road and are too slow for them. It is just a mindset that is ingrained within them.