[dkarl]

I'd argue it's more about whether children learn it as their primary language.

I'd say even that can't accomplish much by itself, which is why the other things you listed are so important. A lot of Mexican-American kids in my hometown spoke exclusively Spanish at home, and now as adults if you ask them if they can speak Spanish most of them say "not really." They're embarrassed if they have to speak Spanish with someone from Mexico who has an adult vocabulary and a sophisticated grasp of the language. When your education, media, and social life is entirely in English, you end up so much more capable in English that that's all you want to speak. Even with their friends who also spoke Spanish at home, if the context of the conversation was their English-language schoolwork or an American band or an American TV show, it was more natural to talk about it in English; if there was somebody present they didn't know, it was safe to assume they spoke English; et cetera.