I was watching a video of a European brake test, and the conductor walks the train and kicks each brake shoe with his foot. I don't recall anyone doing this in the USA, and I actually think it would be unsafe. Anyone have any further explanation?

Actually, he was either checking for flat tires, or considering buying the train.

We used to do this at IRM, rather than just having the crew just observe brake cylinder piston projection. The theory was that if any of the brake shoes had come off (it can happen) it would be caught before the brake head started grinding into the wheel. The 'real railroads' train crews don't do this during the brake test because they have mechanical forces that do the overall inspection.

We would do the same thing at TVRM after signaling the engineman to release the brakes. If no visible gap was observed, give the sticking brake shoe a swift kick to make certain that it moved. That would quickly confirm that the shoe was sticking to the wheel and that the brake was not actually stuck.