Not much. It only needs to have support for our screwball 4G LTE/5G frequency bands, which are different from the rest of the world Because Reasons (well, some of the bands are, anyway, especially for 4G).
From their specs, it looks pretty comprehensive:
4G supported bands B1/2/3/4/5/7/8/12/13/17/18/19/20/25/26/28AB/66/71
5G supported bands N1/2/3/5/7/8/20/25/28AB/38/41/66/77/78
This should work pretty well with Verizon or AT&T. It'll work with T-Mobile, too, but it's missing support for just one of their 5G bands (71).