Okay, before I release anything officially, below is a link to a zip archive with the required files. Consider this a beta release.
IMPORTANT: As always, back up your original or current database files before using these. The changes will apply to newly created games only. Also, be aware that the new world_default.xml file turns OFF the hard coding of player origins for U.S. leagues. But that's okay because you can still get those defaults in the player origins settings during your league setup.
MORE BACKGROUND
The first names file has remained unchanged except that I copied the Spanish first names into the new ethnicity #37 for North American Hispanics. Also, the Spanish surnames in the names file have not been changed, again other than duplicating that set for the North American Hispanic ethnicity.
In addition, please be aware that the U.S. modern ethnicity and nameset are updated as well. You may notice that the Hispanic racial type is set to 0 for the modern U.S. This is because the U.S. entry in the world_default.xml file has been updated to pull its Hispanic population exclusively from the new Hispanic ethnicities #1 and #37.
OOTP handles all of this stuff in a somewhat confusing way, so just trust me that you'll still get plenty of Hispanic players, all of whom are configured based on real life tendencies among the populations in the countries that tend to produce MLB players, including the U.S. And you'll get some American guys like "Michael Lopez" and "Donald Cruz" who are Caucasian or African but have Spanish surnames that are very common in the U.S. The frequencies of these blended names are adjusted in the namesets so that they appear at realistic levels.
Also, I added a select few Asian surnames like Chen and Chang, which are the most common Asian surnames in the census data and are frequently combined with English first names these days. But these are not set to be very frequent at all for American players, so you will only occasionally see them. Otherwise, I have continued to allow OOTP to handle Asian-American players as it normally does, with their own fully Asian nameset.
If you open the ethnicities file, you'll notice that ethnicity #1 is now labeled Hispanic (Caribbean and Latin America), and ethnicity #37 is now labeled Hispanic (North America).
Please feel free to try these files and share your feedback. My primary way of testing them is to create a new league, use the View All Players list, and then sort it by country of origin. I then review the U.S. players and those from the 'Hispanic' countries to check out the racial distributions and the names. So far, I've been very happy with the results, and I'm known for being a demanding pain in the ass. But, inevitably, you may find, like I do, that you still need to do some occasional maintenance to eliminate duplicate names in a draft pool or modify the odd Facegen or name that doesn't quite suit your preferences.
And please point out any U.S. modern surnames that seem particularly out of place. Occasionally, I still find one that I don't think is realistic, so I remove it from the nameset.
http://www.ootpmods.com/mods/Hispanic_Ethnicity_Mod.zip