EU is currently in the process of making USB-C charging mandatory. Apple is still in denial but they will follow suit eventually, in the EU at least.

They're very likely do it everywhere: https://en.wikipedia.org/wiki/Brussels_effect

It costs quite a bit to have different SKUs around the world, especially when one of the SKUs is for a major market. At some point it becomes more cost efficient to just cut out some of SKUs.

California has the same effect in the US: https://en.wikipedia.org/wiki/California_effect

Cars are not iPhones though, and emissions control systems aren't slightly different models. In particular, Hong Kong has its own special dual-sim iPhone model that the rest of the world doesn't get. Only Apple knows what they'll do for USB-C, but they have per-Country SKUs for iPhones already so it wouldn't be out of the question.

They still try to have a limited number of SKUs. Suica (Japan) and CMDA (China/US) features are not limited to specific SKUs anymore, and the dual-SIM SKUs are available in India and China, two very large markets.

All new non dual-SIM iPhones have an eSIM too, so they're all technically dual SIM now.