I had an Oxford trained instructor in English in College who could reliably pronounce the words Mary, Merry and Marry differently and distinctly within the same sentence. I couldn't. Not then and, after years of practice, not now. She claimed that the spelling in English was perfectly logical, and thaty each word was pronounced exactly the way it was spelled, and was prepared to prove it. Don't look at me that way! She made an exception for names, and I didn't agree with her. She told me that there was no such word as Ghotti in English.
As Sapir says, Language is culture.
The teacher is not the only English speaker in the classroom. If the class is a Kindergarden class in English, the kids will pick up the language from the teacher and the accent from each other and from other English speakers in the population, the same way your ancestors did when they came here. There aren't a lot of second generation Americans running around with a heavy accent that I've seen unless they got here in their teens or later. Even then, a lot of them lose it. As the immigrant picks up the American culture through tv and the various other avenues available, the accent goes.
In England, I found it disconcerting to hear guys from India speaking with a cockney accent, but you would hear that every now and then. And in Scotland, you'd hear the occasional Chinese lady speaking in a Scot's burr.
You folks going to tell me that George W. Bush was speaking Spanish with a Castillian lisp? And that his grammar was great? Any Republican Spanish-speakers were simply thrilled that he spoke any Spanish at all. If he'd spoken Spanish enough to be fluent, they would have been so happy they would have had to go to the hospital to get the smiles chipped off their faces. Any problem with accent would have been nothing to them.
I wonder how those Arizonans would feel if the accent that they were having to cope with were a thick Georgia accent, a thick Italian accent, a thick upper class English accent with the various differences in language that the English English speakers feel correct. What about a French accent or a Bulgarian accent? A heavy Boston Irish accent? An accent with clear Black roots?
Any one of these speakers can speak a fluent English, as can a person with a Mexican accent.
Any one of these folks can sometimes speak more fluent English, and sometimes better English than "native Arizonans." Their grammar may sometimes be better. Their vocabulary may sometimes be better and their sentence structure may sometimes be better. So what is this "fluency" being tested against? And how?
Racist? Not Racist?
Who's doing the testing, what are they being tested against, and how do they compare to the population at large? How about some objectivity to start out with before we start firing people and before we start hurling charges around.
It does sound racist to me, personally, by the way.
But it would be hard to say without knowing about what tests were used, how they were applied, and who took them, who scored them and a lot of other data. Where might this data be found?