The thing is, Sakoku passim, you can't really prevent homogenization without entirely abandoning the 20th century (heck, 19th century!) travel revolution. You'd need a global ban on air travel, TV, and Internet.

The alternative is a sort of re-enactment/cosplay approach where people consciously try to keep local traditions and minority languages (e.g. Gaelic, Sami) alive.

Long distance traveling was invented much earlier than 20th and even 19th century.