I've wondered myself about checking the trunk of every car driving into the airport at SHV.
The trunk checkers are not TSA, but local LEO. I suspect, though I'm not sure, that's a procedure established by the airport board, and I don't believe it has any connection to Barksdale. The B-52 base is 10 or so miles away in Bossier City, though some of their planes occasionally use SHV to practice approaches.