Changed Site Address (URL) by accident

It appears there may be two problems with this and it may aid someone in helping me figure this out.

I tried to remove the database and start over for install. It worked somewhat. Except that it didn’t.

I have a domain “behindthescreens.us”
I have it parked at my main domain redirecting into a subfolder on my site “\behindthescreens.us”

When I went to “behindthescreens.cinemasight.com” I could install as normal.

When i went to “www.behindthescreens.us” I got a CSS-less version of the old site as if the reinstallation I was trying to do didn’t exist. I have no idea why they aren’t pointing the same place or how, with the databases emptied and the old themes and content folders deleted, it could still pull the old data (post names, not necessarily post content).

So, I did the install at behindthescreens.cinemasight.com and everything looked good until I changed the site URL back to https://www.behindthescreens.us and everything went haywire again and now I’m back in the exact same spot I was before. Is there something I need to do to fix the addon domain or is this something I can fix with the wordpress install?