If Sander dominated the border regions of Texas it was due to Hispanic's active in the democratic party and primaries. Dominating the primaries doesn't mean the general election which includes all, Democrats, Republicans and independents.
Since Tejano's tend to vote Republican, they most likely voted in the Republican primary instead of the democratic one.
It's high past time that we start electing Americans to congress and the presidency who put America first instead of their political party. For way too long we have been electing Republicans and Democrats who happen to be Americans instead of Americans who happen to be Republicans and Democrats.