In my country, it's a huge success. People love it at the point that even Aldi and Lidl implemented the system.
But, the huge difference with the US is cultural. People coming here from abroad have a hard time to make local friends. It can take up to 10 years to make one.
My guess is that people love the lack of social contact more than self checkout itself.
If you are talking about Germany, yes. I recently (3 years) moved to Germany and I love the tech. I can avoid having contact with the rude people that usually work at the tills.
In the US people working the tills are usually TOO nice and you don't want to make smalltalk with them. Only in NYC have I encountered rude till people, and even there, most are pretty pleasant.
Yes in the US honestly I feel anxiety thinking about the cashier being too nice and not responding appropriately friendly enough haha, there is such a pressure for good service for any retail worker that I feel like it's somewhat rare for them to be straight up 'rude', at most they will be quiet. Like you mention though it does vary a lot region to region from what I've seen.
it's usually better implemented here. i regularly went to a real (the supermarket chain) once, they had one employee manning 4 self checkout machines and one of them took cash. they would open them during lunch rushhour, so all of the people who just wanted a sandwich were out of there within 30 seconds. worked awesome.