If you want to go on tour of the Americas, it is going to take some serious planning. People coming in from overseas often plan things out months or years in advance. It's usually not as simple as shipping your bike over and going for a ride as vehicles from overseas would need inspections and certifications to ride on US roads. What I have seen many travelers do is simply fly to the US and buy a new or used bike here to start the trip. If you do that, then you're looking at a long term trip to maximize your time and make it a worthwhile experience. By long term, I mean months. People will quit their jobs for a trip to the Americas. If you have family here or can borrow a bike like what Phobman did recently for his family from New Zealand, then it should be easier to plan around.
The western part of the United States is by far more scenic and most people coming from overseas usually start out there. Alaska is on my list of places to ride, but I'll need to get some off road experience under my belt to comfortably make it there. Other areas include the entire pacific coast, Yellowstone national park, and all of the national parks around Southern Utah, Arizona, Colorado, and New Mexico.
In the US and Canada, getting around will be very easy and you will never be too far from food, gas, or medical services. If you a long trip, you will have to think about bike maintenance and plan stops accordingly.
2012 Yamaha Super Tenere
2001 Honda Blackbird
2007 Honda 919
49/50 visited on two wheels. 1 more to go!