Roman history shows us an empire, right before her fall, which had weak and corrupt leaders who had overtaken the seat of government. WEAK and CORRUPT -- remind you of anyone???? Probably not. Baaaaaaaa!
Rome was plagued by constant infighting... (Red states, Blue states... liberal, conservative... progressives, constitutionalists)...
Her military was over-extended... (our military is in Afghanistan, Libya, and posts around the world)...
But most startling of all, Rome increasingly became an empire of heavy urban centers...
In America today, only about 2% of the population actually works the land. Our age of industrialization has stripped the countryside of farmers and small family farms, creating an influx of people into our larger cities, and replacing those farmers with corporate giants who utilize improper farming methods (planting the same plants in the same fields, year after year), who rely on chemical pesticides, herbicides, fertilizers, and most importantly, genetic manipulation to produce their nutrient-deficient crops, all which are beginning to result in fewer and fewer adequate crop yields.
Keep ignoring all the things happening around you.