They all have good automakers. Each country has an excellent manufactuer.

Japan quite possibly makes the best, *in general*, cars to today. They are engineered nearly aswell as German cars. But German cars tend to be overengineered nowadays. Mostly because the idiots at Chrysler joined Daimler. Know DCX is draining all that money and putting it in Mercades. They are too good to be true. That 'forces' a lot of other German manufactures to give more for the money like MB is doing. Sad but true. AMC, the cool Jeeps, and the real Hemis are probably gone forever... Japanese cars on teh other hand offer a lot for the driver. Honda (yes, don't laugh you fools) offers not only some of the best motorcycles in the world, they make some of the best ULEVs around. And they also offer semi-great and great driver cars aswell. S2000. NSX. Even the American Acura line up has some pretty good deals.
Europe is usually on top of everything and they make, by far, the best cars, but in general, Japanese cars tend to offer nearly as much with out the higher price tag, which is usually, on Euro cars, their because of gimmics and fancy 'junk' that's not even worth is most of the time.
American cars used to be on top... But sadly in the 80's and early 90's things kinda went downward... for the car fan atleast... GM and Ford are selling a bunch of trucks and suvs which are great vehicles but where in the heck is the tradional rear-wheel drive 2-door sports cars? But, good news....

American companys have finally gotten off their rear and changing things....
Oh and AMERICAN companys sell awesome cars round the globe and not here.... that's gotta stop... I'm sure some American's would like an Escort Cosworth... a Falcon XR6/8, or an HSV Clubsport R8... !!!!
To answer the question... I say America has the best Automakers. They just aren't usuing their full potential... like idiots.
And Europeans always make great cars...
But (!!) if you what a great car, with above average everything, and an average price get a Japanese car. The Acura RSX-S, Subaru WRX, Lexus IS300, and Honda S2000, are all great drivers cars that give you thrils and fun with out a $70k German price tag.
... I'd rather have a pony car though...

lol