Originally Posted by MSPeconomist

I'm confused by your reference to a customs checkpoint exiting baggage claim. The OP will be arriving from Canada and almost all Canada to USA transborder flights do CBP PRECLEARANCE just after checking in on the Canadian flight, before being permitted to board the flight to the USA. At that point, USA CBP officers will see the OP's luggage, checked and cabin stuff (although it's likely to just be a picture of the checked bag which the passenger identifies as part of the procedure). Then, upon arrival in the USA, everything is like a simple domestic flight, with no customs control after baggage claim as the bags will arrive onto a belt with other domestic flights.