If I wanted my laptop to be able to access the Internet anywhere in the US, what wireless ISP should I use?
none that I know of. The best you could probably do is dial up via your cell phone.
Outside of airports, there really isn’t a nationwide wireless ISP.
As for cellphone access, emptor that caveat, my friend. I had a brief flirtation with Verizon’s service, and you need to be in a data service area, which is a sub-set of their digital service area, and certanly not coast-to-coast. If you’re in a data area, the service is fairly good - recall having 64k connections most often.
Earthlink has a service that costs $299 plus $19.95/month. It looks like they have most metro areas covered, but the “wide open spaces” aren’t covered.