Completely agree with you, danuffo, except in the part that having some regional languages in some parts of Spain is NOT a problem for us (it's only a problem for crazy secessionists that pretend to speak only Catalan). Anyway I'm from Seville; my region is monolingual. We have much regional accent, though (sort of similar to Cuban, but without so much intonation).
I agreed with the problem of too many foreign English words in the speech of some Mexicans that are too careless about speaking grammarly Spanish, but I don't think Mexican accent is grammarly downgraded: maybe with some low-classy people that speak too slangy and are not capable to speak more formally, nor write using dotting symbols, that happens. But I think the grammar is the same, no matter how many slang words you put, how much you add -ito, or if you use more indigenous words, or even some English loans more than in standard variety.
Anyway, let's go back to the topic!