I have done the "buy a bike in Europe" thing and believe me, it is almost impossible.
1. A local address (not too hard to get if you have trustworthy friend).
2. An EU driving license to get insurance.
3. The EU license to get the registration renewed because no insurance valid in the country in which it is registered = no registration.
4. EU motorcycle experience to get anything resembling affordable insurance. Go back to #2 and #3 above.
Yes, you may eventually get an EU license, but in many cases that will take 2 years and in many cases you must be a resident to get the license. You can get an International Driving Permit, but that's not a driving license that will be valid for insurance. The Int'l Permit is to help foreigners who dopn;t read English understand that you do have some kind of valid driving license.
Yes, you can get Green car 3rd party liability only insurance for the bike, but it's only good outside the country in which the bike is registered. Green Card insurance is not valid to get the bike registered because it is not accepted in the registration "home" country.
To sell the bike (realistically) it will have to be returned to the country in which you bought it. EU rules make it almost impossible to sell a bike in a different country. First there are import duties to pay. Second, the bike will have to pass local homologation tests (it has to be legal just as though it was purchased in the "new" country). Farkles like exhaust and suspension mods are a no-no when the homologation office checks it over for registration in the "new" country. UK left hand headlights are a no-no in the right hand drive world, so you'll have to adjust them or replace them, according to what the bike will tolerate.
It's a better deal if you have a good friend to store the bike - just ship your bike over and leave it with him, re-register it in the US each year and enjoy your rides. Get Green Card 3rd party liability only insurance and it'll be good in the EU. You can get that for 30-60-90 days or whatever you need so you don't need to insure it when not riding it. Your US insurance isn't valid in Europe.
I've given you the overview. Below are two links to the info for Belgium. If thata seems restrictive, go check the regs for another country you are interested in on the Internet for motorcycle licensing and registration/ownership particulars. It's a nightmare unless you wish to lie about a lot of things.
Look here carefully:http://brussels.angloinfo.com/information/transport/driving-licences/driving-test/
IF you figure a way around all the regs, please let me know. I bought a bike and was told by a local I could get it registered and insured "No Problem".
WRONG! Now I have the bike and I got Green Card coverage for when it's not in the home country, but now that I have to renew the registration with proof of home country insurance, I'm stuck. I may have this solved, but I won't reveal how until it's done.