Visiting the US for a while, I recall being yelled at by an inland border patrol guard in Texas for having the temerity to keep my passport in my trunk. Saying my name was definitely not all that was required.
Land near the borders (particularly the southern border) is treated differently (very poorly, as you unfortunately learned). Texas is not even the worse in that regard, as hard as that may be to believe. Arizona takes that shameful crown: http://en.wikipedia.org/wiki/Arizona_SB_1070