Will a region change reset my hidden MMR

I moved from the UK to the US and i’d like to change my region. I got approved for it and as I was going to confirm it, I got told my rank would reset. I haven’t played comp this season, but I have played last season and before, I was always diamond/ascendant.

Will a region change reset my hidden mmr too and will I start back in iron as if i’ve never played comp?