Originally Posted by
Blumie
On all flights from LHR to the U.S. (and in fact on all international flights to the U.S., except for flights departing from select airports where passengers clear U.S. immigration and customs prior to departure), one must claim their checked luggage, clear U.S. customs, and then recheck the bags...
This is changing, in a few instances. If you're making an INTL->INTL connection at a few airports (MIA, DFW, possibly others) on AA and maybe others, your bags get tagged as being in transit, and they're transferred to your connecting flight without your having to collect them in the U.S. You still have to go through US immigration & security.
This doesn't help OP, however.