Second, the early United States did not face any severe geographic challenges. The barrier island system and local rivers provided a number of options that allowed for rapid cultural and economic expansion up and down the East Coast. The coastal plain -- particularly in what would become the American South -- was sufficiently wide and well-watered to allow for the steady expansion of cities and farmland. Choices were limited, but so were challenges. This was not England, an island that forced the early state into the expense of a navy. This was not France, a country with three coasts and two land borders that forced Paris to constantly deal with threats from multiple directions. This was not Russia, a massive country suffering from short growing seasons that was forced to expend inordinate sums of capital on infrastructure simply to attempt to feed itself. Instead, the United States could exist in relative peace for its first few decades without needing to worry about any large-scale, omnipresent military or economic challenges, so it did not have to garrison a large military. Every scrap of energy the young country possessed could be spent on making itself more sustainable. When viewed together -- the robust natural transport network overlaying vast tracts of excellent farmland, sharing a continent with two much smaller and weaker powers -- it is inevitable that whoever controls the middle third of North America will be a great power.

This is one of the most common historical fallacies you see people cite, on this subreddit and elsewhere. Rather than provide protection the Atlantic ocean, Great Lakes, and inland rivers were modes of invasion for the first few generations of American history. Invasion from French, Spanish, and Dutch fleets or at least the fear of invasion was a trend in American history. Even post 1775, the ocean was more a foe than friend. The British occupied most of the major cities during the Revolutionary war. Washington was burned during the war of 1812, the British raided up and down the coast, control of the great lakes determined if the Northern United States would once again threaten invasion and trade in the United States was nearly completely cut off from the world. After the war there was no assurances that European fleets wouldn't once again return to attack the United States, a fact well understood by the Madison and Monroe administrations who spent large amounts of money on coastal fortifications and upgrading the navy. One only has to look at European involvement in Latin American countries in the 19th century to see that the sea was a means of being the victim of superior old world powers. The Civil War again reinforces how the sea could be a means of invasion. The Union was gradually able to strangle confederate trade, and the Mississippi became a federal highway into the center of the Confederacy.

David Hacket Fischer addresses this fallacy in Historians' Fallacies : Toward a Logic of Historical Thought in a manner probably better than myself