America is unquestionably the foremost cultural, financial , and military power on earth. The fact that your best example is a war that america lost voluntarily because they were unwilling to engage in scorched earth tactics is pretty telling. Afghanistan was a quagmire with no real starting goal, no real end condition, and no motivation to fight. If america decided to drop a few platoons into the country and massacre civilians with mechanized infantry and close air support it would have been over in a month, but to what end? It would make them barely better than the Russians who tried to actually use those tactics and didn't have the resources to pull it off.