It's really fun to see people from a country where you the majority of people can walk around with a gun and freely walk into school buildings or supermarkets and kill people worry about security when passengers that have gone through multiple security checks (physical and behind the scenes) go into the cockpit of an airplane...

By the way, FAA is *not* a problem. I've have been in the cockpit on multiple occasions on departures and landings in the US: JFK, BOS, SFO, LAX, mostly on Swiss but also twice on Air France.

The only country I know about which does not allow it in its airspace is Israel. And in the UK there is a rule that every person in the cockpit has to have an operational role. So whenever I am in the jumpseat on flights from/to the UK the Captain tells me "officially your role is to make sure that the gear is extended/entered. But between us, you shut below 10,000 ft altitude".

So the rule comes less from national aviation authorities, but from airlines. Airlines from the US, UK, Lufthansa to name just a few don't allow it. Air France, Swiss and several others do.