Is it just me or....what's the deal???

I don't know if it is just me but I have lived around most of the U.S and I find there are more uneducated "youngsters" in California when it comes to geography and cultures. I have many more examples but I am going to provide ONE that really IRKS my nerves. I used to live in Miami and when I was asked what my Nationality was I would say Nicaraguan and African - American. It was alright...no more questions. HOWEVER when someone (young...meaning from teen to about 25) in California asks me the same question and I give them the same answer they say..."Oh so you're Mexican?". So in my opinion it seems that everyone out here thinks all hispanics are Mexican. Out here if your skin is light you are white, if your skin is brown you are Mexican and if your skin is just a tad bit darker you are black? Are they not taught that there are more cultures out here than Mexican, black, and white? I have gotten that comment from almost EVERY youngster who asks. What's the deal here?