In the Midwest, the small highways are called County Trunk roads.

Interesting. Over here a Trunk road is a major road. Just one class down from a Motorway, which is our nearest equivalent to your Interstate.

We don't get that many dirt roads, but they usually lead to farms and are normally referred to as tracks.

A whole different language.

A few years ago, I was taking a Canadian visitor out and we had just negotiated a fairly complex set of junctions when he asked "How did you know which lanes to take". I pointed out to him arrows and other markings on the road. A lot of directions at junctions are painted on the road as well as having signs beside the road and you get used to it. I noticed when I was in the States a couple of years back, that you do not do that as much as we do. I think the same must be true in Canada as I don't remember markings on the road when we went from Niagara Falls to Detroit.