I don't have a lot of experience of flight over usa, but as foreigner (level 6, working in uk), it was sometime hard for me to understand non ICAO clerance used by some controller and when I said "say again", the answer was same clearance, even faster ...
Oh and you can be English native and be confused with your left/right ...
So I agree, there are pilot cheating about their English test (used to fly east of europe, and some Russian captain were a joke about English ...)
But ATC from native is not always helping (I found ATC in Uk really pro)