A few years ago a Frenchman wrote what the Americans were like from his experience in Afghanistan.
His first point was that Americans are tall, often standing a head taller than their European counterparts. He noted that the Americans were very easy to pick out.
Second, he stated that every military has that one person who is just a waste of air, the general screwup in the unit. However, with the Americans even the most screwed up guy is better trained than those of other forces.
The average American is strong. Very strong. From his base of operations he claimed that the weakest American was stronger than the strongest soldier in the French units. If a unit was in trouble you prayed that an American unit took up the radio call for help. When American forces picked up the call their reply was "sit tight, we are coming to get you." There wasn't any logistic haggling until the Americans were fully committed to your rescue. They came regardless of what the situation was, In fact they wouldn't ask about specifics until they got close to your position and often knew the threats in the area before asking what problems you were having.
He also realized one overwhelming fact. In all other forces, if an officer was killed you're taught to dig in and take a defensive position. Not the Americans. If an American officer is taken out of commission they go on the attack. He realized that American officers restrain the troops under their command, not for their protection but the enemy's. If you kill or injure an American officer, they are coming for you and very little will save you.
Americans are very well organized.
How do you become well organized? Well, first of all their military is heavily based on equal treatment. You don't become a colonel or an admiral because your uncle is the dictator's cousin or because you belong to the same tribe as the glorious leader. You don't become a pilot because your father was a pilot.
You don't advance ranks by suc... offering bribes to your superiors and doing personal favors.
All of this leads to revolutionary concept that your pilots are chosen from people who have great physical and mental shape and the right kind of mindset for being a pilot while also demonstrating actual capability and potential instead of just being vouched in by an uncle because you were causing too much trouble at home.
Same for officers and everyone else and ... surprisingly you get a military organization that is pretty effective. Definitely not ineffective and there's a great esprit de corps in the US military, great cohesion, good morale and good discipline.
And they also practice for war meaning that accidents happen.
They don't just practice for war
They wage war. There isn't a decade when Americans don't get involved in at least two wars. (exaggeration, tongue in cheek) Their armed forces constantly have their cadre of officers with reasonable percentage of people with actual war experience.
They know how their weapon systems work in real wartime situation and how their troops respond when they come under fire and so on. Most countries just hope that what their guesses are would be anywhere near correct and are also often surprised by those little details that you wouldn't think of until they cause trouble in the real world.
They have a vast economy
In fact their economy has been the largest in the world for a long time. It was overwhelmingly the largest before WW2 and while everyone else's economies crumbled theirs kept growing and has grown ever since.
If European Union was a single country it would be the only country to rival US economy. But even there USA is growing away from it.
What this means is USA can cover all the material and human needs of its military without breaking a sweat whereas other countries will and have collapsed under the strain of trying to even remotely keep up.
Live and let the enemies die
Americans don't really believe in self sacrifice. In Europe, Japan and in many other places we tend to tell our soldiers that they need to be willing to give their lives, etc.
American generals have been famously telling their forces to do the exact opposite - let the enemy die for his country, try to stay alive.
This works pretty well for Americans because they can always assume that they have additional forces, reinforcements and all manner of support available if they merely manage to get out of the bad spot and they can expect to win.
In fact everyone else needs to be ready to die because for everyone else it's going to be like that - everyone else is planning their military strategy from a disadvantage and they have to purposefully sacrifice whole units in order to achieve their goals while Americans conserve their units and destroy enemy units to achieve their goals.
For instance non-American military might sacrifice a unit to hold a bridge to cover the withdrawal of a larger force. The rearguard will be utterly crushed; it's just about trying to buy enough time for others.
Americans don't withdraw like this. They are the ones taking the bridge and if the last defender blows the bridge with him Americans build a bigger bridge in its place. Because they can. They actually had three bridges with them in case the bridge blows up, just in case and because there was a discount for buying more than one. The other side probably doesn't even have a bridge.
Summing it all up
Having an efficient and well organized military supported by a vast economy that can fulfill all the material and human needs of that efficient and well organized military where the soldiers are taught not to get themselves killed but to get out of a bad spot and call in fire support and reinforcements to obliterate their enemies with their material superiority leads to the most fearsome military in existence.
Hardware present in this picture are what most countries on this planet can but dream of.
No other military on this planet is as a dreadful opponent as the American military.
There is a silver lining though - if you surrender early enough they'll let you live and feed you, possibly better than your army. The bad side is that they'll likely commence bombing before sending in ground forces so you'll need to survive the hellfire that they rain upon you before you get your opportunity to surrender.