I think the NHS won’t cover him - mind you they would do it for free for an Islamic terrorist on bail over here!
Strange world hey?
My Canadian mother-in-law, and all the Canadians I know are hyper about getting travel health insurance for their trips here. I kind of chuckle at them about it, but I guess it can kind of come in handy sometimes. I know it is too late now, but you might want to consider it for future trips.
I can't understand why. Virtually every American insurance carrier will cover emergency treatments overseas. My own carrier, Blue Cross, even waives a number of domestic requirements under emergency conditions when travelling. I think it would be wise to check with NHS and see what their requirements are. Your son has undoubtedly been paying through the nose for health care since he started working, and there's no reason why he shouldn't be able to get benefits simply because he got sick while travelling in a foreign country.