I guess we should go back in time and remember this country or the lands the US now ocupy belonged to the natives americans and it was the uninvited british who came "ilegally" to kill and take what didn't belong to them.
After that US colonists took almost half of Mexico.
History continues and now the US has been invading as many countries as they wish for this or that. Now "ilegal aliens" come here because their countries are basically screwed, they are good to work ilegally if somebody can exploit them, but they can no remain here because they're all bad bad people stealing our jobs and endangearing our livelihood.
So, illegals will continue to come to these countries, no matter what. It's just a consequence of the system by itself. As long as we continue impoverishing other countries, their needed people will continue risking their lives for a "better" future.