I have Swedish language Windows 10. And US english speech recognition language downloaded. But I can't change any language settings (since I have not change default windows language I guess). I can't train voice or touch any settings. Speech recognition works quite bad, in game, for me. (I speak english US very good, I've lived in the US for 6 years, so I don't think it's my accent. It's almost like Texan).   

My question. Does this program/addon force me to run English US language, in order to run good? What is your thoughts on this (people who run this addon with a non-english language windows?)

I don't have a non-English version Windows, but my understanding is you have to change your display language to English before you can train your voice and select English for the speech recognizer language.

You may then be able to set your system back to Swedish, but don't hold me to that.  I get different stories from different people.

https://fs2crew.com/fs2crew-voice-control-setup-help/