For the first half of our nation’s existence, our military primarily focused on true homeland security. The Monroe Doctrine established that the USA would focus on concerns in the western hemisphere, while allowing Europe to deal with Europe, Asia with Asia, etc. Such an attitude saved us from being involved in many fruitless wars in other nations.
After problems in Lebanon went bad, Pres Reagan pulled our troops out and sat down with Casper Weinberger and Colin Powell, and came up with the Weinberger Doctrine. This meant we would not go into any conflict unless there was a clear US interest, clear entrance and exit strategies, etc. It was a common sense system that lasted until Bill Clinton sent us into Serbia/Croatia.
During WW I and II, we found that sometimes we are brought into others’ wars. Occasionally this seemed inevitable or necessary. And sometimes we must protect our allies. However, our entrance into wars always had unintended consequences: Woodrow Wilson divvied up Europe in such a way that we had to return many times to “fix” the problem, such as in the 1990s with Serbia/Croatia. Entering into Vietnam with advisers turned into all out war and then spread into other countries, destabilizing them, as well. Because of our entrance into that war, we enabled Pol Pot to gain power, and then slaughter 1.5 million of his own people. Desert Storm led to escalation of terrorism and issues in Afghanistan, Iraq, Libya, etc.
Currently we have over 700 bases overseas. Some are very big Cold War era facilities (such as in Europe), while others are just ammo depots that are almost never used, or are maintained by local contractors. We can save $10-20 billion annually by closing 1/2 of these sites. That is $100-200 billion over a decade.
Next, we return to the Monroe and Weinberger Doctrines and pull our troops out of active engagements throughout the world: Aghanistan, Iraq, Libya, etc. We would save at least $200 billion a year, or about $2 Trillion in the next decade. And this means we avoid new conflicts that are not in our interest. It doesn’t do us any good to leave Afghanistan if we then go directly into Iraq, Syria, or who knows where else.
We become the beacon of liberty again. A city on the hill, as Pres Reagan saw us. We show all others the way to freedom by our example, not by force. As George Washington hoped, we become friends with all, entangling alliances with none.