About a 9.
I can only remember a very few times I felt safety was a real issue, from drivers or people rambling about a campsite. Most drivers were willing to pass me safely. As an example, there's about 10 miles of TransAm on interstate (the U.S. equivalent of motorway or motorbahn) in Wyoming. The shoulder was 12-20 feet wide, and yet almost every truck driver who could moved over into the left lane while passing so I wouldn't get the wall of air shoving me to the side.
Especially if there's two of you, you'll be able to manage some awkward situations easily. You'll develop a sense of what's normal (honest, law-abiding, friendly, caring people); when that feeling changes, one of you watch the bikes while the other one goes grocery shopping, or you keep going to the next town, or you get a motel room that night and sleep with you and your gear behind a locked door.
There are a few specific things you can do to increase your chances of a safe trip. One of the big ones is you don't answer questions about where you're going (on down the road 'til we find a good spot is a safe answer). Other things are just common sense; don't do the things that would get you in a fight in a bar or pub.
Our media is full of horror stories. For the most part, it's because we have a media market that's 2/3 as big as Europe to choose from. I.e., a young girl was abused by her mother and kidnapped by a teacher! Terrible indeed, but was that from around where you live or was it from 2,000 miles away? In the U.S. media, they don't care as long as they get a response from their audience. The range that affects a cyclist is pretty small; if you can avoid panic from a bad thing happening halfway across the country, or halfway around the world, it's a pretty good place to tour.