I believe you can import anything you want, as long as it is non radioactive...
You'll have to pay taxes plus import duties... If the problem is the government, as long as they get paid (with taxes obviously), they will probably allow you to do most everything...
Here in Spain, you have to pay 16% sales tax on all imported goods, plus an imoprt tax of 4% if it is for a car or related. This 4% is like to protect the local automotive industry :-/. Then you have to register the vehicle and insure it (you insure the car, not the driver... weird isn't it?).
I imagine importing something to the US would be much the same.