Illini_Fan
Contributor
As with almost everything, there are exceptions. I did a trip to Grand Turk a couple years ago (so things might have changed since then) and I connected through MIA on my way to Toronto. I have a NEXUS Card, my traveling companion did not and neither of us had to claim our luggage in MIA. It was routed from PLS all the way to YYZ.
I believe that this thread was about connecting domestically in the US coming from an international location. The international to international transit via a US Gateway is not something I have experience with. That truly might be subject to a different policy.
Also, the experience will be totally different if the international airport has a per-clearance facility.
Preclearance Locations | U.S. Customs and Border Protection