The United States does not have an official language
It didn't until a few years ago. The official language is now English. Was changed only recently.
Both things will happen in about 15-20 years.
You're right. Millions of muslims will flood into Europe in the next 20 years and outnumber the Catholics and Protestants. Nice try. Even if a Muslim flood came, I guarantee it wouldn't go smoothly. Some people would end up losing it and wars would ensue, and considering that the Christian countries are the most powerful in the world, game over for european muslims.
(thats only IF it happened, which it won't, not in 20 years. 200 maybe, but not 20)