Is there such a thing as "Mexican" Spanish, or Colombian, or Cuban for that matter?

In advertising... not really. Even in Mexico there are 100's of accents, slang terms and regionalisms to contend with. It's like saying I need copy in American English. Is that American from Texas, Louisiana, or New York Brooklyn perhaps .... see what I mean?

So, unless the campaign is running in that specific region or country, you'll need to find options. Here's why:

There are two basic types of Spanish in every country, the first involves slang terms and regionalisms, the second, is the formal Spanish dictacted by the Royal Academy of Spain, which pretty much every country follows in terms of spelling and grammar.

In US advertising/marketing, the Spanish you use depends on the brand, the campaign, the audience, and message you're trying to convey. Are you wanting to use slang to target a specific audience? Or would you rather sort-of-not-leave-other-Latinos-out, and go with a more generic Spanish? There is no place in the USA where there is not a melange of Latinos.

It's complicated to say the least, and slang although tricky can be very effective when done correctly. Explore different options, get creative and try not leave other Latinos out.