New primitive crossing in Big Bend has an opening date. I chatted with the Park Service several months ago and they weren't sure about the legality of bringing a motorcycle into the USA at that crossing, but did tell me that there was nothing they would. Do to stop anyone from leaving the country with a bike. Of course, this presumes that someone either has a boat large enough for your bike or that the river is low enough that you can ride across.
https://www.federalregister.gov/arti...ry-description