Most undocumented immigrants in the US each year are visa overstays, rather than those that crossed the border illegally.
Likewise when you hear Republicans (and far too many Democrats) talk about opioids and the Mexican border, the vast majority of opioids are brought into the US by American citizens, not migrants.
The worst part of all this is that so many of these misleading or false talking points are spread by CBP and ICE officials that know better.