Those are all gigantic cities, Portland is about as big as the largest city in my country.

There are far, far more cities below 200k and in those its very hard from what I understand. Even some large cities with 500k people have really bad public transport and bad bike infrastructure.

And to live a car free live, you need to live reasonably close to the center where housing is very expensive. From what I understand, the places that are best to live for walk-ability are usually the most expensive.

I've been to Austin and while you can definitely live without a car I don't think it's going to be ideal. It's definitely a grid city that's optimized for cars. I'm not sure about Boston, it's pretty spread out as well but it's enjoyable to walk in, I still wouldn't compare that to any city in Europe.