Texas borders just one country (besides the US), that's Mexico to the southwest.
Texas
Spain
Portugal, France, Spain, Netherlands, and United Kingdom
The Red river forms Texas southwest. The Rio Grande forms the southwest border between Texas and Mexico.
Spain came to the area in the 1500's and colonized the southwest. This resulted in the Native Americans of the area and the Spanish mixing into one culture. In the 1700's Mexico took over the southwest. So, as you can see " Mexicans didn't come to Texas" they were all ready there. Texas came to them. It was southern American's who came to the area we call Texas because they were afraid that slavery would be outlawed in the states.
How is it there? Well, it was established there (as Southwest Texas Normal School, then Southwest Texas State College, then Southwest Texas State University, then to its present name), and it hasn't moved.
It had already annexed Texas from the Republic of Texas, but it gained California and the American Southwest in the Mexican American War.
Spain.
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Germany
Southwest started in Texas.