Most of us here are Americans and are saddled with a uniquely American inferiority complex. Not just toward Britain (our old colonial masters, whom we never should have left) but also the whole Old World.
We walk around in cities that may as well have been built yesterday from a world-historical perspective. Y’all basically trip and stumble over world-heritage cathedrals and monasteries and crap like that anywhere you go.
Like most expressions of hate, it ultimately comes from a place of jealousy.