That would hobble his career considerably. The US is the world's biggest TV market.
To be clear, that is an incredibly unlikely scenario. The incident - in which Clarkson is accused of punching producer Oisin Tymon after the latter failed to give him hot steak dinner - is incredibly minor. It's hard to believe that the police would bother bringing charges, or that the prosecution service would take it all the way to trial.
The case will probably go away on its own.
Even if Clarkson could not enter the US again, it probably would not reduce his appeal as a TV star. If Clarkson went to work for ITV, it could raise the value of that company by £2 billion, analysts say. Part of that value may be tied to Clarkson's ability to promote his shows to foreign audiences - and not being able to to go to America, would handicap that.
The obvious wrinkle here is that Clarkson has already admitted he attacked Tymon and tried to apologize for it, according to the BBC's internal investigation. That admission would make it a lot easier to extract an assault conviction from the presenter, in theory.
And the fact that Clarkson allegedly used anti-Irish language while attacking Tymon ads a little legal icing, too: Assaulting people based on their identity is a hate crime. It could be very difficult to gain a work visa in the US for a person convicted of a hate crime in the
Again, this would be merely the least-likely, worst-case scenario.
In the meantime, Clarkson would be well-advised not to enter the US through Boston or New York, where US law enforcement officials are frequently of Irish-American extraction.