Too many nerves spent on this. So here are the steps:
1. In the Region settings select culture you want to set.
2. Go to the Administrative tab of the Region settings:
3. Then select Copy settings and check both “Welcome screen and system accounts” and “New user accounts”
4. Create new application pools for each existing app pool and assign web site to the new one. For some reason old application pools won’t receive new settings as everyone’d expect.
This was checked on windows 10 pro version.
