"Is it as important to learn Spanish in the United States as it is to learn English here in Argentina?"
Well, no.
But why shouldn't it be? Within the US, why isn't language given its fair share of attention and promotion, along with "core" subjects like science and math?
A Pew study projects that the American Latino population will comprise 20% of the entire US population by 2050. Although Spanish is the most commonly taught foreign language in secondary schools, and maintains a majority in college language classes, it isn't given the same level of importance as other subjects.