Wrong, right, wrong.
SF's Chinese district is almost purely tourist oriented. The most dynamic aka 'real' Chinese districts right now in N. America are Vancouver and LA. These are the places were you get super competitive restaurants because of the discriminating clientele ie Chinese.
Ditto for Mexican food. Tex-Mex is ok, but traditions for the real stuff are imported along with the real illegals in SoCal.
You're right about the Mexican food. Until very recently, we never had any Mexicans in Texas.
my favorite: barbequed onions in (not-sweet) chocolate mole...
best *indian* food i ever et was in Edinburgh, Scotland.