Answer:
A) As both regions are really close together, the climate is almost the same in both of them (Dry, hot), and this also means that the crops and livestock are similar in each side of the border.
Those regions where, back in the day, "property" of Mexico, but now are of the US, so in those regions you may see some cultures that are similar in both sides of the border, for example some dishes.
B) The most obvious thing is the language spoken, and despite the thing i said before about some cultural things being similar, also there are others that are really different, like the most "American"/"Mexican" parts, like clothing, music or other things like that.
