If there was a monopoly situation (which of course is a big "if") then it's reasonable to have laws requiring specific levels of service from the airline. It's fairly easy to write those laws to force the airline to fly.

If the Chinese state intervenes in US domestic travel affairs then the US has the option to nationalize their fleet. All their assets and operational staff are in the US and the staff aren't going to oppose keeping their jobs...

Unless they are the only option - which should be a matter for the antitrust regulators - it's not really a threat, just an inconvenience.