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