Damn those Mexicans! Obviously they're much worse drivers than we superior Americans!
You really should listen to an automotive enginerr.
He will tell you that vehicles a designed for a certain carrying capacity.
When that capacity is significantly exceeded, things like the suspension and handling of the vehicle are seriously impaired (as well as stablility).
As the article noted, vehicles containing illegal entrants are typically overloaded, increasing the risk of accidents.
I again note that it is interesting that lefties have no compassion for the deaths of illegal entrants and don't want to take the necessary steps to prevent such deaths (and the deaths of others on the roadway that they make kill/injure in an accident).