The most successful applicants from the US are creating opportunities for themselves, not only participating in existing clubs/research/sports/competitions.
Some may also do those things, but the US has opportunity deserts, too. Those kids max out the rigor offered, gets high test scores and grades, and then find things to do.
In your situation, industrious kids would pursue one of the volunteer opportunities, then possibly initiate a new program within it to address some unmet need…or be the best student volunteer ever. If their thing is humanities/sociology, they can document a history of their town or something in it and ask a high school teacher to do some oversight. They could create a podcast/recording of a historical walking tour of their downtown that the chamber of commerce could offer to visitors. They pursue their interests in whatever way they find.
Some kids do have more opportunities than others in Mexico, in the US, and everywhere. While it may be impossible to level the playing field, intellectually curious or socially motivated kids will find or create an outlet.
You may do all of this and find later that you didn’t get into an elite college, but it will still be worth it because you followed your interests, learned something, and contributed.