Netflix do the bare minimum, which is region detection. That's the industry standard procedure. Hulu does the same, but even BBC iPlayer, which offers content mainly provided by BBC themselves I think, can be tricked in the same way as Hulu and Netflix.
At the end of the day, it's very hard to regionally lock anything on the internet. From Amazon to Steam, to Sony themselves, people very easily access content from all over the world. Nintendo from all companies are probably the ones who lock out content better, haha.
Sure, Netflix could lock accounts to a region forever, but that would mostly make that most people around the world would just sign up to the american Netflix and not their local Netflix service.