Why is there such selective enforcement?

I'll bet they understood you just fine and just acted that way.

seen it with Spanish speakers and with the French Canadians, when I ran up there in the 80's and 90's

 

Depends on the company's authority, i believe. Some can do long haul in the US and some can get a 'zone' authority which are the ones just dropping at the transfer warehouses in places like Laredo.

TransMex, for example, is Swift's Mexican long haul company. I saw them in Iowa frequently for some reason.

 

Oh, if you meant the language barrier, it's absolutely ignored lol. Especially if they're an international driver. Very subjective on what's considered knowing enough English and way too frequent of a thing to ever be cracked down on. Too far too gone, just like 1099 misclassification, double brokering, etc.