Photographs of 19th Century Japan

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.

Speed and scale of long-distance travel are obviously the relevant factors, not just "is it possible to go far".

Air travel is faster than horse, and carries more people.

Here's an isochrone — travel time — map from 1881, centred on London. Note the legend uses tens of days to measure time: https://en.wikipedia.org/wiki/File:Isochronic_Passage_Chart_...