Hi pepper! Glad you're enjoying Cogmind, and that's.... a very weird issue
I actually have no control over adding keyboard layouts--that's a Windows thing and seems to be happening to other people on Win 10 as well. (I'm assuming you're on Win 10, because I've never had any issues with layouts on Windows before but now I too have had trouble with it automatically messing with my layouts, since I have a lot of them, but the US layout happens to be one I use as well.)
So this is something you'll have to address on the OS side. For example see
this post on the Microsoft forums.
(Maybe it's detecting that Cogmind's underlying engine uses the US layout and decides to add it to the OS? (even though I don't think that's really necessary) No idea, but this is the first I've heard of this.)
Let me know how it works out for you!