I'm willing to bet the passengers on any of the airplanes that have been subject to terrorist attacks in the past few years would have been willing to undergo a full body scan if it meant the bad guy couldn't get on the plane with them. Full body scanners also don't care what country you're from, if that means anything.
I think you're confused. By agreeing to the body scan, you aren't trading privacy for security. You are trading privacy for a lack of privacy and a security theater performance. The body scanners don't find the "bad guys" or the tools that the bad guys allegedly use. They do grossly invade personal privacy, violate constitutional rights and further inconvenience innocent civilians. Just like removing your shoes, pat downs and bag searches.
I like how you understand that fear can be used to motivate passengers to give up their rights. Even if they're statistically safer flying than anything else they'll do this year. Successful terrorist attacks on aircraft are scary and make the news companies lots of money, but they're also so rare they're practically non-existent.
Any effort spent trying to stop the terrorists that already successfully made it as far as the airport security screeners is a waste. They could just as easily attack the security checkpoint, the bus they road to the airport in, the school, mall or library on the way to the airport, or any other target.
There are far fewer terrorists in the world than you would like to believe. There aren't enough resources to guard every possible target against every possible attack. Guarding anything less than everything is ineffective because a terrorist can just attack whatever is left. Guarding only against attack strategies that have already happened, or arbitrary imaginary ones from the movies is also ineffective, because a terrorist can just come up with a new strategy at very little cost, while the cost of protecting against each thing is huge.
If you want to protect against an invisible enemy that can attack anywhere, at any time, through an means, you have to do it proactively and logically. You have to identify the enemy, their source and motivations before they plan and implement an attack. You don't want to waste resources and burn freedoms trying to guard against them after they're armed and at the gate.
Even if you could guard every target against every possible attack. Is that police state one you want to live in?