I believe there is a threat. The huge waves of new Latin American immigrants are not being expected to speak, or learn English. I was recently at a student orientation for middle school children, and their parents. They had a Spanish interpreter who interprted everything the principal, councilors, and every other speaker said. No other language has ever been so catered to in this country. Spanish is provided at about every customer location, voice mail system, etc. Many schools provide bilingual education programs.
If you don't think that is a threat to our country, consider why Quebec has been on the verge of seceding from Canada for the last ten years. It's because of the language difference. We are also on the verge of becoming a bilingual society, and that will balkanize our country, particularly the southwest.