Only PWC required Green Card but it is just for entry level position. Other three are available for international student. My four classmates have began their work at big four. All of them are Chinese.
As far as i know, the starting salary for MAcc graduates from top schools ranges from 50k-70k. I have a undergraduate accounting classmate going to PwC with a salary of 50k. In addition, The reputation of schools DO matters. Thinking about the alumni network and the quality of the program.
If the stating salary for MAcc is only 40k, no one in America will go for a MAcc becuase undergradute starts alreasy from about 40-50k. CPA will help you increase your salary about 10-20%.