The USA is a very good country to tour by bicycle. Some states are better than others, but generally, the roads are good and wide and minimal traffic, you have alternative routes to escape traffic, beautiful scenery, reasonable prices, friendly people. I recommend USA bicycle touring for everybody including Americans who have not fully explored this country.
As you pointed out, Japan is very good. China is excellent. France is wonderful - very bike friendly.
One of the worst countries I have ever seen for bicycling is Italy. The roads are absolute death traps for bicyclists; ultra narrow roads, no shoulder, winding, and the drivers speed on these roads with no concern for what is ahead of them around the corner. Even walking in Italy is a white-knuckle experience. Yes, yes, Italy has good food, friendly people, nice sights - all true, but very bad for BICYCLE touring.