This cuts both ways.
Sure the chinese guys need better english - but I tell you one thing the Americans can REALLY do with better more standard english.
I am native english speaker and mostly have to really concentrate when american controllers speak to me. They generally assume you know your way around their airport and their slang - which is mostly not the case. I fly around the planet to 40 different destinations and might see JFK once a year!!!
American controllers should realize that the average pilots world is a bit bigger than the average controllers backyard.