More like deranged and/or a victim of disinformation. The US-Mexican border is one of the most aggressively controlled borders between countries that aren't at war in the entire world.

It's easier and less expensive (before interest and other predatory student loan fees, at least) to get into an Ivy League university as an American than it is to legally enter the US as a Mexican.

As for undocumented immigrants, most of those are people from Europe and Canada who entered legally and then overstayed their visas.

The amount of people crossing the Mexican border illegally is absolutely miniscule in comparison, but Mexicans and other people from Central and South America tend to have more melanin than Europeans and Canadians, which means racist Republicans fear and loathe them.