The American public and parts of the democratic and republican parties are dangerously naive about international relations' role in homeland security.
If you disengage from the world like progressives, and pareo-conservatives want you to, the world is a small place, and any country can build a drone, develop an ICBM, or straight up just shoot American tourists.
Let's say we leave our hundreds of known military bases, and use our navy to guard the US. We take all American companies, and tell them to shut up, and put jobs in America, and only America.
One scenario of what would happen is that some power like China would take over and control the world's oceans(that is the least bad of our options), and they would become the most powerful country in the world, and we would stagnate in power, well-being, and technology. And it wouldn't be all sunshine, and rainbows because in the beginning they would encounter beginner problems with their Navy, and soldiers who would die in the thousands against drone attacks, and attacks on shipping. All the countries with a grudge against the US would start building ICBMS, and start handing them out like candy to proxies, and we could see cities in the US being hit by ICBMs from say North Korea because just like the bomber always gets through, some ICBM, drones, and terrorist attacks would always get through.
Another scenario is some fascist country-based power like Turkey(Just an example, I don't know who would reach their apex in a less US ordered World) would conquer all countries with no nukes in their region, and start getting more resources, and eventually when they start conquering, and conquering, and conquering, and reach Europe, and we could see European countries and said fascistic power start nuking each other, conventional wars, and or just genocide of some group in the fascist empire.
The worst scenario is some jackass like this guy would start handing out nuclear technology like candy to countries that hate the US, and they would hand nukes of their proxies, and we would see a nuclear attack on an American harbor or City.
en.wikipedia.org
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There is no disengaging from the world, the real children are people like Tucker Carlson who thinks once the US leaves the world alone the world will leave us alone. That's not happening.