Do passport cards keep track of how many days an American stays in?
First of all, I apologise for not knowing what a passport card is, but I do know what a passport is. When you use a border crossing, you talk to a guard. While talking to the guard, he or she is typing information about you, and sharing the information with the US border agents. You can hardly realise what is happening, but this is how they do their stuff. One important thing everyone should be aware of, is to NEVER LIE TO AN IMMIGRATION OFFICER. A smile from them means very little.