Which issue related to mexico became controversial beginning in the 1990s?

Illegal immigration was really never a problem until the 1990's. Not because it didn't happen but because nobody really saw it as a problem until racist's started seeing it as more crime and all those dumb lies. And it's not Mexicans only that immigrated, it's also people from central and south America. All illegal immigrations are just dreams, dreams of human beings wanting better lives and a better future for them and for their family. I am very grateful and I love my grandpa SO much for that and manyyyy other reasons. He left all his life behind in Mexico when he was 13, he migrated to literally a new world all by himself thinking of his future family, his evolution, ME! And all at the age of 13! 13 years old! He worked and still works very hard because of his dream, his dream to be happy and have a happy family. I could never thank that man enough. I know that all this is way too much for a simple question in school lol but i just wanna get that message out to people, so yeah, that's the answer and my opinion and story on illegal immigration lol Have a good day XD