1. Both were once part of Mexico
2. Both were independent republics before joining the US.
3. Both have fabulous historical sites reflecting items 1 & 2.
4. Both states are huge, geographically speaking.
5. Residents of each state think they live in the best of all possible places, not just on this planet, but possibly in the known universe. Ask them. Neither can fathom why anyone would want to live in the other state.
Texas, however takes its state pride to a slightly different level than California. Furniture stores in Texas often feature pieces with the Lone Star emblazoned proudly upon them. You don't see many Californians looking for furniture with the Bear on them. Texas even has its own pledge of allegiance, which from what I have heard, is often recited in schools along with the national one:
Honor the Texas flag;
I pledge allegiance to thee,
Texas, one and indivisible.
Perhaps not Pulitzer prize-winning poetry, but it's straightforward, clear and to the point.
I did a Google search, to see if California has its own equivalent. All I got was references to news articles and court cases about people in California trying to ban the national Pledge of Allegiance because of the words "under God". A similar Google search for the Texas pledge got notably different results.
And here we begin to see some of those differences.