As a minimum, demographic should concern you. European culture, violence in India, Russia, the Phillipines and elsewhere are all threats from shifting demographics.
And if you're still a hardcore protectionist, consider this:
American Muslims have children at a high rate.
Non-Muslims American are barely at the replacement rate.
Your great-grandchildren will be under Sharia law.
"Your great-grandchildren will be under Sharia law." -- Kidd
"It's hard to make predictions, especially about the future." -- Yogi Berra