As a European with several motorcycle trips behind me in many different countries in Europe I have to agree that it is easy to travel by bike in Europe, the general public is normally friendly (even in France), and the distances are not too great between alps, mediterranean sea or whatever you prefer. I once went from Mediterranean to Baltic Sea in 22 hours. You don't have to be hesitant about most countries of the old eastern block. Poland, Czech republic, Hungary, Slovenia for instance is no problem to ride in. My personal favourite country to ride a bike in, has to be Scotland. The scenery is as good as in the alps, the roads are super (not that they're bad in the alps) and the people are great. For you Americans there is the advantage of language, and of them being more used to your silly units (hey, isn't it time to realise that the French did something good when they invented the metric system?)
A country that is supposed to be just as great to ride in (but slightly more expensive) is Norway, where I have never set my foot on two wheels, so to speak. I have heard great things, and seen great pictures, about the roads and scenery there.
One day I hope to go to America for a biking holiday, I can certainly recommend you guys to come here. Welcome!