.US is a bit of an oddball, at least compared to gtlds. The US DoC puts rather strict requirements on the registry under contract, including this but also spot

.US is a bit of an oddball, at least compared to gtlds. The US DoC puts rather strict requirements on the registry under contract, including this but also spot checks that owners are US citizens, and makes it the responsibility of the registry to take action on it. Those scans are automated but supposed to have human-in-the-loop, though that doesn't really mean much either. Unfortunately, once the process starts, receiving no response means an automatic suspension.