ask your friend a simple question: How many illegals WANT to become US citizens?...and do they expect to give up their other countries allegiance?
“...and do they expect to give up their other countries allegiance?”
they don’t have to give up citizenship of native birth any longer - dual citizenship is now the name of the game.
in the days of yore when I was first involved in law enforcement, new citizens had to renounce their prior citizenship. (I mentored someone through a very lengthy process in the 50’s)