<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by The_Diamond_Z:
You get to stand in a really long line, but otherwise no harm done.</font>
This is only true if you have your US passport with you. If not, you will be presenting a foreign passport which has no entry visa. If, like me, you live in a country from which one is required you will be refused entry.