To get an american car you have three options:
Go to the United States, find the car you like, put it in ship (better on a cargo container) and get crazy with the homologation and taxes you have to pay.
Buy it to an import shop (they do more or less the same), but pray if you have a problem with the car.
Buy it in the official dealer: GM sells here the Cadillac Seville, CTS; Chevrolet Corvette, Alero, Trailblazer, Tahoe and TransSport. Ford sells only european models now but the old F150 (before the Explorer).
In my case, i bought the Pontiac imported from Germany (it's a bigger market for american cars after Sweden), and the Blazer from a person that imported from the USA a couple of years ago.
About going offroad: in some places you can't go off the road, and you can't buy a permission or anything. In other cases you can go, but with rescue equipment (they use to check it). The last case: you pay a "tax" in some places for one car, and in others when there are 3 or more cars together.
Car modifications in Europe are very restrictive, everything that wasn't in the car when the dealer sold it has to be homologated (the builder has to pay quite a lot of taxes), if not it's forbidden. That involves you can't touch almost anything in the car. So we don't see too many modified cars around, that Blazer of the photos atached is the most you can do.
The photos are of a trail i did the day before the photos were taken (by an offroad club in Madrid).
PS: Sorry for the mistakes i could make in my english and for the long post