Ah, my point was more that if the action being taken isn't "get planes on the ground _now_" and so the US airspace remains open for traffic already in the air, then it's unlikely they're trying to get international planes to either divert or return.
This definitely feels like 'unable to manage normal volumes at normal speed' rather than 'unable to manage anything.'
In which case freezing domestic (and the huge amount of load it contributes to ATC) but keeping international normal makes sense.
Of course... the side effect is the "fun" that creates for incoming international flights with domestic connections...
> (Sure, a flight near the Canadian or Mexican border could in theory divert to a Canadian or Mexican airport, but it's unlikely many people on those flights have their passports with them.)
There must be some procedures in place for this - I pretty regularly take domestic (Canadian) flights that pass over the US where I don't carry my passport.
A domestic US flight can still divert to Canada. There usually are special arrangements that allow people on a diverted flight to stay short-term while the situation is resolved, even if they don't have the required documents or visas.
(Sure, a flight near the Canadian or Mexican border could in theory divert to a Canadian or Mexican airport, but it's unlikely many people on those flights have their passports with them.)