This is interesting claim...I agree with you up to a point. If polish doesn't necessarily equal white it doesn't rule it out, and there's a complicating interaction between self definitions and the responses of others, subordinate or dominant. Its situational. Here in Connecticut during the 1980's the INS regularly harassed Polish ethnics in New Britain and routinely raided businesses hiring immigrants whose entry into the U.S. was, how shall we say, creative. But the Puerto Ricans or Blacks in central CT knew that these new arrivals not only made an easy transit to white but aspired to it.
Euro-ethnics get a lot room for manuevering, ala symbolic ethnicity. They get the real or imagined solidarity but can junk the identity if it gets too costly.
Dennis Breslin