Let me correct you on that. Everything going into the U.S. is not checked. It's not 100% testing at the border, no. The Americans do spot checks the same as we do. They also do equivalencies of plant processors and have almost like a NEXUS card for people travelling. They give pre-clearance to plants that have measured up to the U.S. standard. That's the difference.
They don't measure everything at the border, as some people claim they do.