The U.S. doesn't recognize Taiwan as a state, but that's how it's typically shown in the U.S. Though it's also quite easy to see various alternatives. And Taiwan is hardly the only example of this.

The U.S. has no laws requiring specific depictions, nor does its government cajole movie producers to depict regions in certain ways. Many countries are similar. Map makers choose borders largely based on what they expect their audience wants or needs.