I feel so bad for my doorman friend (US citizen but not born here). He had plans to go to Miami to visit family and then to El Salvador to visit a friend. He didn't realize that his passport expired so he did an expedited application. Didn't get it, didn't get it, and so went to the office. He was told that they wouldn't issue a passport due to nonpayment of child support from 1989. Thing is, he was cleared of that in the 90's. And, he was allowed to go to the Dominican Republic to bury his son in 2005. Stupid bureaucrats. So now he's not going on his vacation.
So you know the current rules and regulations.
Customs and Border Patrol Web Page