When Biden was president he opened the border to anyone from anywhere and gave them all welfare. The only difference is that they have to come here first.
When you set up a situation like that you will attract everyone who can figure out how to get here. And they will come in droves from everywhere.
Knowing how Democrats work, if Biden's open border policy was allowed to continue it would on be a matter of time before Dems started offering welfare to those who want to come here but can't. And then it will be a short hop to just giving welfare to the planet.
Dems close their minds when it comes to doing the math on that kind of stuff. The just think that we have to do it because it is humane. Everything Dems propose is humanitarian to everyone except for us poor grunts who have to work just to pay for every Democrat failure.