I think it's simply illegal to build housing like Tokyo does in every US city, and often every project over 3 stories needs community input and faces environmental lawsuits over things like shadows
For nearly every maximum or minimum that the zoning and code sets, flipping the direction would be better. Have parking maximums instead of minimums. Have density minimums rather than maximums.
Make those who want to have too much parking get exceptions and be vetoed by a handful of people showing up on a Tuesday afternoon meeting. Let those who want the "luxury" of low density living in urban cores be the ones begging the neighborhood busybodies and control freaks for the chance to under build in prime locations.
1) clarity of law without local community process that overrides what the law says you can build,
2) extra capacity to actual build. Almost 100% of land is "built out" according to zoning, meaning that almost no land allows building anything more than already exists. In fact this downzoning was so intense that many many buildings would never be allowed to rebuilt, including iconic buildings.
We have literally outlawed cities in the US, due to the wishes of people that want suburban automotive lifestyle to replace city life.