Buy a car in EU - but can I ever bring it to USA? (Brussels)

I may finally break down and buy a car here in Belgium. if I bought something that is sold in the USA - a VW golf, BMW 3 series etc, could I actually register it in the USA ? Whats been your experience ? is it hopeless ? I did not being my cars here from the US because I was afraid they would be to expensive to register and run (think big engines, big car)
Finally I know I could bring anything 25 years or older - so maybe I just but a 20 year old since I may be here another 5 years or so !!!
Or is there someone here with a car they brought from the US that they dont want to bring back and wish to sell ???