Dude, I'm a Special Forces officer working at US Army Special Operations Command. While I certainly don't know everything, I feel very qualified to speak on this topic.
You are discounting the volume of people there are in the world. Think back to our lessons in Korea. Think back to the lessons that the Nazis learned in Stalingrad. There are countless other examples of this as well: You can't discount sheer numbers. Technical superiority is great, and training can make your guys force multipliers. But when wave after wave of shit comes at you, then you are going to feel the pain. That's what made the kamikaze pilots so dangerous in WWII. That's what made vehicle-borne IED's so dangerous in Iraq. That's what made the Chinese so tough to defeat in Korea. Wave after wave of these things keeps coming at you, and you just can't kill them quick enough. Even with nukes, you can't kill them all quickly enough. Eventually, the swarm breaks through. We even saw this was a warm game done in 2002 that was theoretically designed to test us against the Iranians. Even with low tech, the bad guys sent speed boats packed with explosives and suicide helicopters, and in the games, they sank a huge portion of a fleet of warships.
On top of that, you need to think about supply lines. How are we going to get that many supplies to everywhere in the world all the time? It's logistically impossible. We can't project forces to reinforce efforts that quickly either. We also aren't designed to train a competent force that fights literally everyone in the world.
Honestly, this kind of bravado is a position of ignorance. It just can't be done. A reasonable leader should never fight more than one front at a time. You can sometimes get away with two fronts, but damn, that's taxing. Smart strategists don't divide their forces like that.