This article on History News Network compares the current state of the United States to the Roman Republic a few decades before it fell.

By the second century B.C., the Romans believed they had achieved the ideal state: a republic with strong checks and balances that provided a voice for the common people while limiting the dangers of direct democracy. By the mid 140s B.C., victories in foreign wars had led to a massive expansion of Roman power. It seemed the Republic — stable, powerful, and immensely wealthy — would last forever.

But things changed. The economy transformed as Roman power expanded across the Mediterranean. As Rome began to import cheap grain from North Africa in quantities previously unimagined in the ancient world, grain prices plunged. Domestic small farmers were squeezed out of the market and off their lands. Rich landowners snapped up land from these struggling farmers, incorporating these plots into giant plantations worked by slaves from newly conquered territories. Many of these land acquisitions were illegal — but the plebeians were powerless to stop them. Forced to compete against slave labor and facing a nascent form of corporatization that favored the wealthy, the plebeians felt that they were cast aside as Rome ascended to greatness.

In response to these changes, the plebeians voted a slew of populist politicians to power. These politicians were called Populares. While some Populares genuinely sought to uplift the plebeian class, others learned to harness the power of the people in a cynical ploy for power.

– See more at: http://historynewsnetwork.org/article/163207#sthash.FccCVUPn.dpuf

Could the U.S. form of government really fall? I am not predicting that but I can envision a scenario where it is plausible. Let’s say a completely incompetent leader gets elected by the people (I’m not naming any names) and orders the military to do something so egregious it refuses to carry out the order. At that point, the Constitution would no longer be functioning, so what then? Congress could act quickly to impeach the President to maintain the appearance of order, while the military could temporarily maintain order until the Vice President or another civilian leader could be installed according to the letter of the Constitution. But if that sort of thing kept happening, the Constitution would be weakened each time until one day the civilian government might cease to exist. Sound far-fetched? Maybe, but within the realm of plausibility. Throw in some serious natural or industrial disasters, terrorist attacks, or major geopolitical conflicts and it could put even more strain on our system.