First time I've been driving from San Diego to Phoenix and encountered an immigration checkpoint along I-8. I pull up and the question was "Are you a US Citizen?"

I know it was more of a behavioral profiling question, but a bit surprised that the question was phrased that way as opposed to are you a legal resident or something. Quite a few people I suppose would be answering 'No'. I just wonder if that that point they have to produce some documenation besides just saying they're on a visa or Greencard.