Ok, i have read through many of the posts and all the talk about red states and blue states is moot. There is no country on this earth capable of coming into this one and taking it over. The United States is too big, the geography too complex, and the people too diverse. Look at previous civilizations that have failed like the Roman Empire and more recently the U.S.S.R., what happened? They lost control of everything except a much smaller, central location. Geography is super important, i.e. mountains, rivers, deserts, etc. New dividing lines will be formed. Don't forget people of like mind and history will be more likely to stay together/be controlled than forcing groups who are polar opposites together. Many of our states are as big as countries in Europe. It is likely the United States will break-up into several countries with a central area remaining.
