To quickly summarize, zoning is of course what you can or can't build on a given space. In the US, this is almost exclusively controlled at the local level. In Japan, it's mostly at the national level.

In the US, the zoning process isn't simple. We can have hundreds of different zones that attempt to micromanage even what kind of stores go on which block. In most of America we have exclusionary zoning: only this kind of thing can go here, everything else is disallowed.

In addition to zoning, we have lots of other planning rules. How far a house is set back from the street, minimum acreage, maximum height, parking requirements, floor area ratio (FAR).

The net effect is that much of America is unwalkable. Your closest grocery store, gym, office, etc. is in another zone. Your house has to sit on at least half an acre, so that would mean longer walking distances and a smaller customer base. Buildings can't front the sidewalk due to setbacks.

You have to navigate a sea of parking because the urban planners said that your store must build enough parking to handle Black Friday, even though most of it is unused every other day of the year. Oh, and it must be free.

When you build, you must navigate all of these complicated rules. Because it's all at the local level, your neighbors are empowered to protest and stop the process, because your neighborhood council has the power to stop it for arbitrary reasons, mostly codewords to keep "others" out.

All of these things have an environmental and economic cost.

In Japan, it's much simpler. There are way fewer zones to choose from. Most zones that include anything other than residential only will include all uses considered to be lesser nuisances in addition to whatever new uses it allows. For instance, a commercial zone also allows residential. A light industrial zone allows commercial and residential activity. Some zones, like heavy industry, only allow that single use. This is due to fire and safety needs.

Japan also has FAR limits, setbacks, etc., but most of these are based on something rational: shadows. The idea is that, without special exemption, casting shadows on neighboring properties is bad and heights, setbacks, etc. are all based on this. Japan as far as I know doesn't push things like parking minimums, so builders build however much parking they think they'll need.

The net effect is that much of Japan is denser than America. There are way less tall buildings than you'd imagine, but it's uniformly medium density until you get out into the countryside.

A lot of errands can be accomplished with a quick walk or bike ride. Because of the density, public transit can actually be run at a profit by private companies, who make money on real estate as well as transportation. That is, incidentally, the reason why systems like the New York subway were built: to make money, especially via real estate.

While Japanese megacities like Tokyo are expensive, they are actually fairly affordable as compared to other megacities like London or New York. The ratio between median income and housing price means that it's possible for your median household to get something. Japan builds a ton of housing, way more than NYC does.

What's great is that if you're priced out of Tokyo, most Japanese cities are going to be fairly walkable given the good planning, so there isn't the "I must live in New York to live in a city" issue we have in America where places like New York, San Francisco, Chicago, DC, etc. all have huge demand because they are the few walkable cities.

The negative to the Japanese system is lack of local control over most things. Japanese localities have some levers, but mostly the national government controls everything. Lots of Japanese buildings are IMO ugly, but there is some architectural experimentation that would be difficult to do in America. For instance, this (close) restaurant: http://okinawahai.com/naha-harbor-diner-aka-the-treehouse-re...

Imagine that restaurant in downtown $AMERICAN_CITY.