USA fails to win the heart of the Afghan people, the same as in Iraq.
It was supposed to be after the invasion, Afghanistan and Iraq economies will prosper.
But it's not happening.
Pretty much every country in the world is already free, and try their best to develop their economy and society, to adept modernity.
Invasion or not, democracy or not, liberated or not, all are the same.
USA invasion brings nothing new to these countries.
It just makes things worse than before, because of war, economy, and social collapse.
And that's how USA fails.
To win the modern war, you should win the heart of the people.
Try to understand their problems and fix them for them.