Are most internet-based sellers are subject to juridiscation in every state where they have a customer?

That depends ultimately on the interpretation by judges of the wording of each state law in question. For as long as people have been able to buy things over the internet, there has been a debate regarding whether those people are required to pay state sales taxes. Companies that have a retail store in the perceived state of residence of an online shopper collect sales tax from that shopper on behalf of the state... as the debate continues. Some jurisdictions prohibit the import of certain items, like some weapons or drugs for example, no matter what their point of origin may be.