I used to go through this routine every three to four months as a child, up until the time that I left home for University. Our family divided the year between residences in Southern Ontario and the Bahamas, travelling in our family "station wagon" (PA-32 Piper Lance), and, as you can imagine, these trips entailed frequent border crossings into and through the US. The OP hasn't described anything remotely out of the ordinary, and certainly nothing that would merit a specific complaint.

I can recall MANY occasions upon which, after transiting MYLS -- FLL, our plane would be COMPLETELY stripped by US Customs looking for contraband. Everything would come out: luggage, seats, panelling, etc., and the entire process could take anywhere upwards of one to two hours. Officers were always very professional (if a little surly, probably at the thought of having to perform a futile search), and we understood that they were all on edge because the nature of their job could be quite dangerous.

I can also recall spending an hour or two on the tarmac of remote airports-of-entry -- Havre and Glasgow, Montana come to mind -- before customs/immigrations officers finally arrived on scene to let us in to the generally deserted airports. We all understood that most officers had to travel from some larger centre, had other duties to attend to, and may even have been off-duty, and were grateful just to have someone be able to clear us through. These delays are unavoidable and just part of general aviation.