I would have to disagree on it taking that long (as in so short) - not the change to zoning law, but the actual existing building infrastructure.

Cities are one thing, and often have better infrastructure in place (though absolutely not a guarantee), but general suburbia you wouldn't find much shift in a short time. For one, availability of sites for new construction, and two, its the most likely place for quick capitalist change (new expensive clothing store rather than say, a small grocer).

Its going to get harder the further rural you get, there is more space but won't be as much appetite. Small businesses had already been squeezed out by the likes of Walmart and their ilk, and wouldn't sensibly be able to return without other changes (like being low cost enough and affordable to the local folks to go there instead of a Walmart Super Center or whatever those giant warehouse mini mall ones are called), which means financial incentives and lower and middle class folks having more money to spend.

Which you'd need to start having people stay more local for work to grow the local community.

Its a part of a solution, but it isn't a solution by itself IMO. And its going to take time to have an impact. Time that will be on a decades-long scale, considering many towns have been around for a hundred years or more that isn't a staggering timeframe, its sensible.

It definitely can't be done in the same kind of timeline as bike lines and bus infrastructure.

(Edit: stupid mobile keyboard)