Why is the border still wide open despite the American publics opinion against this situation? Even under Republican Bush it didn’t change.
I say follow the money. Probably drug cartel money is paying off politicians, judges and police on both sides of the border.
Actually, it's entrepreneurial employers of low-wage, unskilled labor. Perry of Perry Home, Butts(es) of H.E.B. grocery-chain (they're the "B"), Don Tyson the chicken magnate, and many similar self-made men do it like they want to (I think it's part of their entrepreneurial makeup, to despise laws and democracy -- take note, Trump supporters) when it comes to keeping their labor costs low.
The aforementioned people are active and generous members in good standing of the "donor class" who support Republican politicians. Their influence on GOP politics has been, until this year, decisive, and it may yet prevail over us lowly "insurrectionists", allied as it is with the giant vampire squids of Wall Street (Goldman Sachs & co-predators).