Tex-Mex is from Texas... that's what the Tex part is, and it's distinct from Cali-Mex, because while both cuisines originated from Mexican influence into the area using local ingredients and traditional techniques, the ingredients were different and the influences originated from different regions of Mexico which heavily influenced the cuisine. Tex-Mex originated with the Tejanos who resided in Texas while it was still part of Mexico and mostly originated from Central and Northern Mexico while Cali-Mex is predominantly a result of immigration that occurred later on mostly from Western/Coastal Mexico.

Tex-Mex and Cali-Mex aren't the same thing, and California has no claim to Tex-Mex...