USA and Canada. I have no relatives but want to plan an astronomy based holiday.
Where & when are good viewing places to stay? Buy a scope & tripod there possibly to cut down on luggage. Planes, trains & taxis for transport (no foreign self-driving).
As others have pointed out, North America and the countries occupying it are much huger and much less densely populated than what many travelers realize. Because of the distances and low population density outside the larger cities, there is not a lot of public transportation options in the rural and wilderness areas. Even small towns and villages are often too far out to make public transportation economical. The result is that rental cars end up being the main mode of transportation for travelers.
Light pollution will be much smaller in small towns. Everything west of the Mississippi is much more spread out and darker. The great plains are cursed with cloudiness, haze and turbulent atmosphere - making the astronomical views poor. As mentioned by others, Florida and the southwest desert are good.
I would suggest looking at Amtrak train schedules, bus schedules (greyhound and big bus), and scenic tourist train/bus schedules. See what small towns and parks they stop at. Another option is the Alaska ferry system. The ships go as far south as Seattle and stop at coastal and island towns all the way up the west coast to Alaska. The only caveat is that you would be very far north and limited with observation targets as a result.
Acquiring a scope could be the bigger challenge. Covid has disrupted the supply change and most everything is out of stock and on months long back order. If you can't hook up with a local club at your destination, your best bet might be to get a heritage 130 or an ST-80 and stuff it, along with a decent photo travel tripod, into a small bag or pack for the plane trip. Otherwise you would end up probably with a spotting scope or big binos.
As far as safety, most rural folks are friendly and will be helpful with regards to helping you find an appropriate spot to set up - lot less fear, suspicion, and rules than in the urban areas. Animals are the bigger concern. Livestock in rural areas and the cats, wolves, bears, and reptiles in wilderness areas. Also moose, elk, and bison in some places.