In my experience it's the smaller airports, both in the UK and North America that have worse security guards. Flying through Roanoke I was singled out, hearing one officer say "Get the Brit." At which point he ransacked my bag, made me remove my jeans, and searched through everything I had, including tipping out the entire contents of a tin of mints.
When asked "was security as good as this back in Heathrow?" I replied with a smile, "No, back home our security are efficient and competent, not egotists on a power trip." That shut him up and I was quickly advised to get to my plane.