That’s exactly what it is (illegal) except the politically correct far left keep changing the term to what is now “Newcomer”. Before that it was “Undocumented migrant” I forget what the hell it was before that, I’ve lost track. When you Google “Illegal Alien” the results all come back for “Undocumented” this or that, very few have the word “illegal”.
That process is what’s known as the “euphemism treadmill”
https://en.wiktionary.org/wiki/euphemism_treadmill