Idunno. As an Orthodox Christian, I do not observe secular civil holidays, except for July 4 and Thanksgiving. (The latter is not really a secular holiday, and might make a good Orthodox feast day anyway.) (Not all Orthodox follow my practice, either.)
Making muslim holidays American civil holidays would make that many new “holidays” not worth observing!!!! PHOOEY!!!!
Besides that, the only appropriate muslim observances in the USA would be September 11 and April 15 (date of the Boston Marathon bombings in 2013). Phooey again!!!!
If the Muslim days are made Federal Holidays then surely our 12 Great Feasts plus all of Holy Week and Pascha deserve the same!