There are plenty of places in the US where this isn't true, and the number is growing.
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.
The summers are more or less solved with e-bikes: you spend less energy paddling, while still profiting from airflow. I hear France has a subsidy for them. Unless you're in Spain or Southern Italy I guess, or there's a heatwave going on.
I commute on a bike (at least, if I'm not going out after work) in London. I have a foldable Brompton bike fitted with an e-bike conversion kit from Swytch. I can ride in the middle of summer (ok, maybe not in those 40C days we just had) and arrive with no sweat. And if it rains, no matter, I stop, fold up my bike and jump on the Tube, or a bus.
I don't think so. Imagine: two people, each with a job not in cycling distance, and they have two kids at two schools in opposite directions. What do?
It's easy if you get lucky with locations of places you need to go to each day, or (more often) you have enough money to buy your way there, or if you have enough money to buy a place on good public transport routes, but as with most people if you don't, then cars are still the most affordable way to do it.