Many Spanish speakers in the U.S. who learn the language in school (high school or college) learn Castilian Spanish, which is not what Mexicans speak, as the pronunciation is different and some of the vocabulary is different as well. Every country in Latin America seems to have their own version of Spanish (exclude Brazil). The most different I found was Argentina, where the Spanish seems to be mixed with French, Italian, and a little German due to the immigration patterns there. @Chrissy Cross can probably speak to that better than I can. Anyway, most Americans, when communicating with Cockneys or Scots speaking rapidly have trouble, and I suppose Londoners speaking with folks from the Bronx have a similar thing. Churchill said that Brits and Americans are two peoples separated by a common language. I think the same can be said about the various dialects of Spanish.
The Rio Grande Valley in Texas has Tex-Mex. Although most people there speak Spanish, you probably hear Tex-Mex most often. People who are fluent in both English and Spanish can use Tex-Mex efficiently, using the word from whichever language most closely reflects the point they are trying to make. Others will use mostly the language they are most fluent in, substituting words in the other language wherever they want. Although I took two years of Spanish in high school and scored well, that didn't help me at all, more than a decade later, when I moved to Texas, where people actually spoke the language. I did take a crash course in spoken Spanish after moving to Texas, whereas high school dealt mostly with written Spanish. Then I gradually picked up bits and pieces that I needed to treat patients who may not speak English well in an emergency, as well as conversational Spanish from people who I lived and worked with. Although I have never considered myself to be fluent in Spanish, I could get along okay with it. Ten years after I moved to Maine, I came across some migrant laborers who were doing laundry in the laundromat here in Millinocket, at a time when our washer had broken. Thinking they might appreciate finding someone in Millinocket who could speak Spanish, I tried to carry on a conversation and didn't do very well. It seems I have forgotten much of what I have learned, which shouldn't be shocking when I consider that I am forgetting some of my English words too.
I was too young @Don Alaska ....any Spanish I know or learned was in High School in Pittsburgh. We spoke Hungarian at home even in Argentina. I do know that my mom and dad learned to speak it fairly well for the few years they lived there. I remember my mother getting the "Readers Digest" delivered every month when we lived in Pittsburgh and it was in Spanish not English.
I can ask you in Spanish what your name is, where do you live...and I can understand when naughty words are said in Spanish too.