If you look at Europe in the '70s and '80s, it didn't look all that different from the US: just as car-centric, but just with fewer motorways running right through the centre of towns. The difference is that in much of Europe, people gradually started to wean themselves off of cars. These cities weren't "designed for foot traffic": people took actual steps to make them more pedestrian friendly after being very, very car-centric for a long time. The US and Canada can and should do the same.

Many European cities have pedestrian-only central squares or plazas that are hundreds of years old.

A couple decades ago there were cars in most of those plazas.

Actual steps were taken to change that.

You assume that there wasn't a period of several decades where many of those squares and plazas didn't have roads running though them, and needed to be reclaimed from cars, much as streets in general needed to be. That assumption would be wrong.

That's only a tiny part of a city.