We've been through this before, probably more than once. For instance, Benjamin Franklin was definitely afraid English would be displaced as the primary language ~260 years ago when he wrote this: (An excerpt from Benjamin Franklin's Letter to Peter Collinson.)
http://teachingamericanhistory.org/library/document/letter-to-peter-collinson/
Sounds remarkably like the arguments being made today. So, what happened? Is our primary language in the U.S. today English or is it the language Franklin was so worried about dominating and pushing out English as the primary language.....which was German.
In fact, English has become such a worldwide used language, other countries have attempted to curb English's takeover. And it's not surprising, given how English has invaded the world. English is the de facto language of science, aviation, etc. worldwide. And those are just two very simple but pervasive examples of how English has grown to a worldwide language.....this doesn't even acknowledge our music, movies, etc., that are consumed worldwide.
If anyone should fret about their "official" language being overrun, it's everyone else, not the U.S.