In order to enforce a country’s laws and the broadcasters’ licensing rights, the streaming provider must detect where the viewer is located, either to select the appropriate content library or to block access entirely.
As AMC is only interested in broadcasting in a handful of locations, it only buys the rights to show a video in those countries. However, while this more cost-effective, it causes international travelers no end of problems, since they’re effectively locked out of a service they pay for just because they’ve gone on vacation abroad.