The defining moment was the overturning of Don't Ask, Don't tell!
The defining moment for the USA was the rise of the TEA Party Movement and the refusal of accepting an out of control federal government through peaceful protest; unlike the OWS movement which destroyed public property, raped and abused woman and promoted dependency instead of self reliance.
When we bombed Libya and helped overthrow the government there.
The defining moment for the US was the killing of Osama Bin Laden. Like the President said "he was given more respect then those in the Towers were..." Good ridence!