You can wear a hijab in an American passport photo and all identification. The US constitution also states in amendment 1 that all people have the right to practise their religion. I find this particulary amusing because there is currently a thread about banning a website, but in the same amendment for religion it also states the freedom of the press and speech, and California signed this amendment.

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"Diplomacy is the art of saying 'Nice doggie' until you can find a rock - Will Rogers"