It is easy to find many other sources with the same statistics. These as I understand them are people who speak 2 languages and not people who have simply learned some of a second language. There are a lot of American people speaking Spanish in the US, of course there are also for example, 1.5 million who speak vietnamese.

This is broadly true with white Americans when their immigrant background is there already for generations... but a huge part of america does not even speak English at home. America is a melting pot of people from everywhere in the world and they naturally bring their languages, food, and culture with them. It is easy to forget, especially when only looking at specific demographics of a diverse country.