Once you arrive in Alaska, you will encounter the same difficulties before you reach Nome which is the closest town to the Bering Strait. Once you sail up the Yukon River, all of the Americas will be accessible.
If you manage to get this far, then it will be hard to stop! You will probably extend the trip to Patagonia. If you do this, it should be possible to experiment again the bikebo system and cross the Darian Gap which is the area between Panama and Colombia where there is no connecting road..

The blue tracks are either on sea or on river (Unalakleet then Yukon rivers). The other colors will be on land.