If one of America's main exports is culture, why would you ban factor inputs?

They're also not fungible and extremely mobile. People get attached to specific OF stars and the medium inherently requires remote work. So it's an inherently global labour force that protectionism won't help. American OF models won't magically make more money if you ban immigration unless you also ban cultural imports.

The government isn't displacing local talent by importing OF models and gets tax dollars for essentially doing nothing. Those tax dollars pay for schools/hospitals/etc.

OF also skews towards young, unmarried women, which balances the gender surplus of unmarried men that generally tries to immigrate. Since they're young, they also have more productivity before drawing on benefits like Medicare or Social Security.

By any objective standard OF models are the ideal migrant.