Recently flew from a TSA-managed airport (in an American territory, but not a US state) and was surprised that I wasn't required to go through any kind of security check (no x-ray, metal detector, nothing). The inbound flight went through security provided by that country's government.

Is this normal or did someone mess up?

FWIW, the flight was a regularly-scheduled commercial air service, however it was a small plane (Dash 6) and had maybe 13 passengers on board (with no door between pax and cockpit).