taylory2j: The simple answer is that they don�t. The US is now compiling details about visitors to their country. In the past, despite the visa programme, there were too many holes in the security process. All that is happening now is that these accumulated details permits them to more easily identify �known� criminals or those whom they may wish to be monitoring.
Our MI6 and their Homeland Security exchange �some� information, as do other countries in monitoring individuals with whom they all share interest. Fingerprints that may have been collected in , say, the Middle East, where there was the presumption of nefarious activities, could now be flagged when the individual arrives in the states. Additionally, the fingerprint process permits them to associate name details against further identifiers.
The process is as fast as making a photocopy. Therefore, you needn�t worry about delays in processing.
Have a great trip, wherever it may be in the states you�re headed.
Fr Bill