Dear Harlan,
For many important languages, e.g. English, Spanish, French, you name it, we have been brought up into our mother language by our unchosen teachers at home and we all think we speak a neutral form of it.
There are more than 20 Spanish speaking countries, including the U.S. Usually, we are not too exposed to the variants spoke in other countries except for some movies and celebrities, and it's mainly focused on pronunciation. In any case, we all have some small difficulties at first catching up with some usual words and constructions that are different from our home country. That is normal, not so cumbersome and fun to experience.
Try though to learn the standard form of the language, avoid slang, because that is too local and stick to one form of it.
Enjoy your learning.