You can be an Extra where ever you live.
Listen, I want to tell you right off the bat is that you don't need to live in NY or Los Angeles to learn and live tv or film. And unless you absolutely are needing to be a major motion picture or become a TV star right off...the smart thing might be to become part of one of the many film crews as an Extra in a major city near where you live.
Most films are done on Location. And those locations can be in Aberdeen, Keene, Los Vegas, Pakipsi or most any part of the country. And many of these scenes need Extras. And they hire Extras locally. That means either in your town or a city near your town. Sometimes a film crew will just show up in a smaller town, put an ad in the paper for Extras with a time to show up for interviews.
So before moving to LA or NY, check things out first near where you live. It's way easier to learn the language and craft in smaller markets than to butt heads and egos first thing in LA or NY. So How Do You Become a Paid Extra? Listen up!