Even the US has more Spanish-speaking people than Spain.
However, Spain is still very influential in the development of the language. The "Real Academia de La Lengua" dictates the rules, and there's a network of "Instituto Cervantes" throughout the world. There's even one in Chicago, where I live now.
I don't know if you are being serious, but the spanish language is defined by the R.A.E, and it is influenced by other national academies, so it is more or less supposed to be country-neutral. If, say, peruvians speak closer to R.A.E's spanish than spaniards, then they are the ones speaking proper spanish. It is also worth noting that for many spaniards the language we call "spanish" is not their first language.
Say 'cucumber'. The sound of the first syllable is very different from the second, even though both are written the same.
Say 'stake' and 'steak'. Different graphs for the same phonemes.
Say 'E as in elephant'. Two different sounds for 'e'.
etc.
Present day English is so bad that written language is divorced from spoken language, but it is not bad enough to unite all speakers behind a spelling reform.