Actually they well might be.
During my days working for a major British bank, I visited one branch where there were 500 customers who were named "Mohammad Singh" (First branch of the bank to use 'photo IDs) This was in the 60s. Some of today's radicals could be second or third generation.
We have people that have lived here for decades who don’t consider themselves Americans. And if they don’t consider themselves Americans then neither do I.