You will find I reach the same conclusion as in your final paragraph except that I am not blind to the FACT that differentials in IQ between race exist. It's a topic I have looked into extensively and it is just the way it is right now. The average Japanese person has a higher IQ than the average Puerto Rican and that is just a fact. It is not racist. Of course you are going to meet Americans who struggle with tests of intelligence. People will anywhere, but how many will depend upon where they come from, the parenting, schooling, genetics, a variety of factors. At the end of the day if it is too hot in the kitchen and you cannot cook the dish on time then you are not cut out to be a chef.

I know full well what test anxiety is having been designing and administering tests for many years. In truth, you don't see as much of it as you would think. Written tests mostly show what you are capable of. Now oral tests are harder, but again, mostly reflect classroom performance levels. IQ is a different kind of test, but if you have anxiety then you need psychological help of some kind or else simply are not able to do the work. I doubt Americans have more test anxiety than any other groups anyway.