Local language can be used
Every country can use their native language in radio transmissions. (Determined at the same meeting, in Chicago) Now, what is the official language of the USA? (Hint; Good Luck).
Lets call the official language of the USA non-ICAO english, and all the people that complain about R/T in the USA not following ICAO English just lost the argument. No need to file anything with ICAO, as we are communicating in the local language when you do not understand what is being said, much like when I fly in China or Spain.
I am not a native English speaker, but the US is the easiest and most efficient ATC environment I have operated in. (The only place I have not been yet is the Antarctic. Still want to go there as my Grandmothers cousin was the first guy to get to the South Pole and back).
Why not embrace and enjoy our differences? I operate world wide and it is part of what makes my job interesting.
Learn something. Every flight, every day.