Distrowatch lists MX origin as "Greece, USA", but likely have developers from both the US and the EU mainly.

I would not consider MX a branch of antiX. Some developers are also working on antiX so they likely share the same ideology (mainly anti-capitalism), but while antiX is explicitly affirming so, MX, instead, keeps a neutral political tone on its portal and its communications on everything non-linux related.

I had used MX and it is a well-rounded distro, totally recommended in in a computer older than a decade, you don't like systemd, like Debian but dislike anything Ubuntu or if you like any of the specific tools they ship with MX with. Also, knowing the ideology of some of their developers, if you despise big-brother, this distro should be less likely to be compromised than, lets say Fedora or Nobara.