There - right there - is another indication that this is more of a settlement (or resettlement) of this country by Mexico than just immigration, if the natives have to speak their language in order to communicate in their own country.
Considering that most of the western part of the USA was originally Mexican territory...it stands to reason that maybe Spanish should stay as one of the languages spoken.
And...why are you so fearful of a bunch of Spanish-speaking brown people? Is it because they come here, work like dogs, start businesses, make money, pay taxes and generally within 2 or 3 generations become successful? Here where I live, most of the car washing services, smaller restaurants, mini-marts, painting and construction contractors are Latino-owned and operated businesses. My downstairs neighbor owns a car repair company and he does mobile repairs too. His children are bilingual, they're all in school. They live pretty cheaply (I know what their rent is) and he supports not only his family, but his sister's family, his parents and family in Mexico.
If you want the Latinos out of the country, then go do the jobs they do...landscaping, farm work, construction. Wasn't it in Georgia they tried to get white folks out to harvest and none of them lasted an entire day? Truth is, you can fuss all you want but we, here in the US, NEED these people.