<font face="Verdana, Arial, Helvetica" size="2">Just another case of American Xenophobic Indifference. What does it take to make them appreciate this issue. Somebody blowing up Air Force One? </font>
The ICAO mandates bag matching on all international flights. There is no similar requirement regarding domestic travel - it's not the DCAO after all. In the US, the FAA does implement such measures from time to time in response to threat situations.
Once the bag and passenger have commenced the journey, separating them on subsequent segments is not seen as a security risk due to the randomness and unpredictability with which it occurs.
The correlation with xenophobia escapes me I confess, and I very much doubt a 'common' passenger's bag would find its way onto AF1, unaccompanied or otherwise.