I just came back from PTY (did YVR-LAX-DFW-MIA-PTY-MIA-TPA-DFW-YVR), the purpose of my trip was obviously a TP run. Though since I only spent 17 hours at PTY (bordering drug source countries) I was sent to secondary at MIA and subsequently got a frisk search at a private room and then released to continue my journey.

This wasn't my first TP run but the first to a "suspicious" destination in the eyes of every average customs officer let alone CBP folks
Assuming you're just going to mainland US you have nothing to worry about, they know these frequent flyers' practices.