"How do you know?"
Living life with my eyes open. For instance, the FBI is the world's most honest and efficient law enforcement system. That needs no further refutation.
For instance, the US is the world's most altruistic country.
Or that Presidents are admirable men.
Maybe the US military fights only just wars and in a just manner.
The most important thing on Earth is to accumulate stuff.
We're raised with beliefs which are 180 out of phase. True story.