Bad advice above. Your rights as a citizen of the United States do not evaporate just because you step outside its borders, no matter how aggressive and abusive the incompetent swamp of USCustoms & Border Patrol drones act towards you. Find a cot and get comfortable, and then use the smart phone you refused to hand over to them to look up and call a civil rights attorney.
“ Unlike citizens of other countries, U.S. citizens are entitled to enter into, and to depart from, the United States, and to obtain a passport from the government. ... The right to enter and leave the United States is so fundamental, however, that a citizen cannot be prevented from coming into the United States merely because he or she has no passport. Even if someone departs from the country without obtaining a passport, knowing that he or she should have done so, he or she must be permitted to enter upon returning if a birth certificate or expired passport is presented, or if the person takes an oath as to his or her citizenship.”