So I think the good news is, a lot of it can be retrofitted, if there is political/societal/voter will.

It was all retrofitted here in Europe after all.

The infrastructure can be retrofitted, but the fact that cities were designed to be sprawling under the assumption that people would drive is a bit knottier to work out.

True. But if you could get 90% of non-work stuff a cycle ride away (groceries, childcare, post office etc) that’s already a big one.

London, another massive sprawl, opened what’s called “cycling superhighways”. These are on disused railway tracks, covered with high quality tarmac. Wide, straight, lit, off-road, bike-only trails taking you around the city (into the centre in particular).

I wouldn’t call London cycle-friendly but these really make long commutes feasible. A friend of mine, no exercise freak, happily cycles 40 mins each way on one of those.

They are not disused rail tracks, they are on the edge if roads.

Exactly what happened in EU. Many EU cities in the world were designed for cars. So it can be done.

But zoning is also part of the issue. Residental areas many places in NA is often strictly residental - designed around that people can just take the car to go grocery shopping.

In europe it is more common that you have things like a supermarket in walkable distance (or atleast short trip on a bike).

Tokyo sprawls as do many chinese cities but people bike to the train

The city I live in was designed for horse-and-carriage transport. Most of the buildings in the town centre have preservation orders. What's underground is often a mystery - a recent construction project discovered a cellar that nobody knew was there.

So back-fitting cycle lanes is rather difficult, when the roads are already too narrow for cars, and can't be widened.