In a nutshell, it is largely a combination of three things: the hangover from the end of the Cold War, 9/11 and the subsequent “War on Terror”, and the refusal of a number of countries to shoulder the burdens of preserving the global commons.When the Cold War ended & the Soviet Union collapsed, president George H.W. Bush assigned members of his administration, including James Baker & Dick Cheney, with the task of figuring out a new, post Cold-War foreign policy strategy for the United States going forward. Unfortunately, he lost his bid for re-election in 1992 and we elected a candidate with no foreign policy background, Bill Clinton. U.S. foreign policy essentially went on “auto-pilot” and there was no comprehensive effort to figure out what our role in the world should be. Defense spending decreased, the economy boomed, and by the end of Clinton’s 2nd term, the U.S. gov’t budget was in surplus.9/11 drew the United States into an open-ended conflict in the Middle East thanks to the misguided invasion of Iraq in 2003. Support from our allies was middling at best, and the United States shouldered most of the burden of containing the chaos that Iraq devolved into. Defense spending skyrocketed so that by 2011 the Defense Department budget totaled over $700 billion. Obama won the 2008 election largely on a promise to end the Iraq War, but failed to adequately ensure that Iraq would be stable after our 2011 departure. The country quickly fractured into competing factions along ethnic & religious lines, creating a power vacuum that ISIS was able to fill, leading to several more years of war.Lastly our allies, particularly in Europe, proved unwilling to maintain their military capabilities after the end of the Cold War, leading to decades of declining defense budgets that hollowed out their armed forces. Russia’s annexation of Crimea and their ongoing efforts to undermine European stability have awakened the Europeans to just how vulnerable they are and to how intimidating their idealism & “soft” power is in the eyes of Vladimir Putin.Which brings us to the present. A certain level of isolationism is natural to the U.S., since we’re on the other side of the world from Eurasia, where 68% of the world’s population, and the lion’s share of instability and the struggle for power, is located. The United States could easily draw back from its’ involvement in the wider world, our economy is not nearly as dependent on foreign trade as the economies of China, Japan, or Germany, and much of the foreign trade we do engage in is in our hemisphere.We are now self sufficient in energy thanks to the fracking revolution. The U.S. will likely become the world’s largest oil producer this year, having already become the world’s largest natural gas producer. Thus, we have no compelling reason to deploy our Naval assets to keep the straight of Hormuz open, or to get mixed up any more in the never-ending carnage driven by ethnic & religious hatred that characterizes the Middle East. A nice little balance of power struggle has developed as Iran, Saudi Arabia Turkey & Russia work overtime to undermine one another in a futile quest to dominate the region, and no doubt continues to fuel the tide of migrants desperate to reach Europe. The allies that we spent decades protecting, including South Korea, Japan, & Germany, are now standing on their own feet & more than capable of defending themselves.Global trade can only be maintained if there is a Navy willing to protect global sea lanes. If the U.S. Navy restricted it’s mission to protect American trade only, other nations would be forced to dramatically ramp up their naval capabilities in order to ensure the free flow of goods to and from their shores. Take Japan, for example, they must import almost all of their oil & natural gas, and the oil tankers headed to their shores from the Middle East must sail through the South China & East China seas, areas that are being contested by China & several other countries. If the U.S. decided to withdraw it’s Navy from East Asia, Japan would be forced to dramatically bulk up the size of it’s Navy to ensure the free flow of oil & gas from the Middle East, and to diversify it’s suppliers. They would also need a powerful Navy to ensure the safe passage of Japanese goods to the rest of the world.Germany is another example. Despite their clean energy initiative, the Energiewende, Germany’s dependence on energy imports continues to INCREASE and is now close to 2/3 of their consumption. 40% of their oil and 35% of their gas comes from, you guessed it, Russia:Germany’s dependence on imported fossil fuelsHypothetically, if the U.S. withdrew their forces from Europe, leading to the collapse of NATO, and Russia decided it was high time to annex the Baltic states, Belarus & Ukraine, and to destabilize Poland, how much of a fight do you think the Germans would put up, considering their dependence on Russian energy, as well as the massive amounts of foreign investment that German companies have in Russia? With Russia having annexed the Baltic states, what do you think would happen to the E.U., considering that Estonia, Latvia & Lithuania are members? How many harshly worded condemnations issued from Brussels would Vladimir Putin listen to before erupting into uproarious laughter?The same principle applies to a number of other countries. The bottom line is: our alliance structure is out of date and no longer serves U.S. interests. We can withdraw a large portion of our overseas deployments and not be adversely affected, since we are now energy-independent & our economy is not overly dependent on exports. However, the rest of the world, having grown accustomed to U.S. security guarantees, would be abruptly thrust into fierce geopolitical competition in order to secure their interests. This re-arming of the world would create tremendous opportunities for U.S. arms sales, no doubt, as it did prior to U.S. entry into WWI & WWII. It would also create a flood of foreign investment as the rich from all over seek a safe haven for their money.Thanks to the Shark-in-Chief who now occupies the White House, the rest of the world has been put on notice: a growing number of Americans, sick and tired of overseas entanglements as well as the ongoing chorus of anti-American sentiment even among our so-called “allies”, is in favor of a withdrawal, even if it creates massive power vacuums that unscrupulous actors are willing to fill. It’s a cynical viewpoint (& one that I don’t share, but find VERY tempting), but it’s gaining strength by the day: that U.S. power should protect U.S. interests only, and anyone who desires the U.S. as an ally needs to pony up some serious dough. Trump is still waiting for Frau Merkel’s check to arrive in the mail.