Tiny Houses aren’t allowed (and won’t physically fit) on every road and highway across America. If you’re worried about low overpasses, bridges, and weight limits, the best way to avoid these sticky situations is to purchase an RV GPS. You simply upload the stats of your tow load (weight, height, width, etc), and the GPS navigates reroutes you accordingly.
I used the Rand McNally GPS for my 25,000-mile roadtrip, and I had very little trouble with navigating. In fact, it saved me from having a comfortable Tiny House plenty of times!