I don't believe that's the way it works. Your example implies that the flight attendant was employed in the states for their job, but just flies to other areas of the world.

I think my position is more of a "foreign worker". I am a US citizen, but a Belgian resident. I start a job soon, and will be paying income taxes into the Belgium tax system from that job.

The flight attendant in China for 2 days on a layover only will pay sales tax and maybe a tourism tax at the hotel in which they will probably stay.