I visited a Target store in Madison Wisconsin and that was the first place I ever discovered magnetic wheel clamps on shopping carts. So it exists in the US... it's just not super common.
Living on the West Coast I see carts all the time that have the wheel locks, they just don't do anything.
As a person that has been a cart pusher, carts suck. The wheels, especially at the front where they put the wheel locks are the first thing that break. They barely touch the ground and spin in circles all the time. Stores rarely ever invest in fixing or buying new carts.
I firmly believe that many places in the US simply gave up on it, because what happens instead is people still try to steal them, drag them a great distance damaging them, and they have to go get it anyways. I think we had maybe 3 good carts at the Sam's Club I worked at our of like 200 or 300 carts.
