China to Rule the World?

       If we are to fear the actions of a country outside of the US, shouldn't we move our fear the actions of a few angry people in a couple of poor countries to a real threat with money, numbers, and legit ways and means to attack us, like China and many of the other countries of the East?  They have the resources, money, and real weapons of mass destruction. The only thing holding them back is the ability to grow enough food to feed their numbers.  If they were to take over the US, they will have more than enough land to grow all the food they need; and there populace is educated at a greater level in high school  than most universities in the US educate their students so they would be able to outwit us through technology and other equally valid advances .
       What stops this very real threat from attacking us while we are weakened and spending billions on a war  of little real consequence? Plus we are now financially indebted to them through our borrowing of billions to help bail-out ill-managed US companies.  I really want to know what is keeping us safe?