The Liberal Mind, We fought a Civil War that answers your question and I am content to abide by it. However, had I been of the era I might well have supported a States right to secede from the union quite independent of the reason it may wish to do so.
As to California becoming predominantly Mexican and adopting Spanish as its official language by previous response still holds. We speak a common language for the same reasons we speak any language and their are many pragmatic reasons to do so as a country. The country would not suffer as much as would California.