I know these were all tounge in cheek but.....
London Heathrow handles the most international passengers (as opposed to passengers on domestic flights, which make up the majority of traffic at US airports). On an overall scale including domestic flights carrying smaller passenger numbers per flight, Heathrow ranks third behind Atlanta and Chicago
Someone beat me to it, but LAX is FAR busier than LHR, and you can fly right across the top at 2000 talking to LAX tower if you want, or if you can't be bothered to talk to anyone, go across at 3500/4500 and just squwark 1201....Oh and if you decide to land there, you'll pay $20 (or it used to be)
Of course you could also add in the other 30 airports within a 30 mile radius as well if you wanted....
Thud, there are probably more GA accidents/mid airs/airproxes in one week in the US than there are in the UK in one year
If you checkout fatalities per 100,000 flight hours, I think you'd find the US far safer (and they don't have the OHJ)