There are many threats, national bankruptcy, comets striking earth (which we seem unprepared to prevent), infighting, terrorism and the extremists here who fight to prevent it. I think the biggest threat though is the proliferation of weapons of mass destruction. It amazes me most every nation and large military contractor does not have afomic weapons which are 70 year old technology. The weapons should be getting smaller and my that border with Canada is long and easy to sneak across much less deliver militarily. Throw in EMP and biological weapons and it is a scary world of advancing technology I believe we have as on whole spent tons of money to keeps tabs on world wide amazingly well. The political / psychological effects of the use of such weapons would be terrible also. Consider the change in our landscape after 9/11. A whole voting block was created who somewho love small government but love the huge Patriot Act (to over simplify). Besides more money dumping into National Security and allowing clun constitutional clandestine activity I don't know what to do about it. Maybe I have watched "Sum of all Fears" too much lol. What is your largest worry?