What would the legal consequences be for PornHub if they ignored the law and didn't (and perhaps don't) have any physical or commercial presence in North Carolina, beyond the website being available?
They sell an online subscription. Some states consider there to be a nexus if you’re selling to residents in the state. NC doesn’t tax digital software, so that would complicate things, but it wouldn’t be as cut and dry as “we don’t have a physical presence there.” Fighting the government, even if you’re right, is very expensive.