Yeah if EU / US tries to mass conscript citizens, but migrants and illegals are left out of it...

That's not gonna go well. Whether the conscription is successful or not. Lotsa unrest.

Even if you manage to conscript 1000's of Middle Eastern troops. They are the worst soldiers on Earth. No military training program in those countries have worked. Whether it's western or eastern approach. You'd have to go full commissar mode, rather than honor doctrine.