Mandarin or English.
Spanish is not the language of money/finance/power. Too many Africans and Indians are fluent in English plus other languages. Chinese will learn Mandarin and English. Many Europeans speak English plus one other language.
You would need a China/India/Russia type country speaking Spanish. Mexico, Argentina, Spain etc., ain't moving the culture like that.
Plus, Latinos barely speak Spanish after a generation in the US. After a generation or two, they go from Antonio Ramiro Romo to Tony Romo: