Hi Federico,
look at this:
http://www.grandamericanadventures.com/tours/american-rockies-holidays.html

I was planning a tour with a similar route to the one you say. But without the driving...
I point you to this link (is an escorted tour) as a suggestion of a route from Seattle to Yellowstone. If they can offer it, it's viable.

In any case, driving in the USA is easier than in Italy or Europe (I'm from Spain). And less stressing.
The only 'problem' (in fact, not a problem at all) is to get used to automatic gear change.
Oil is a lot cheaper than in Europe. And roads are well maintained: USA is made for drivers!

About the route, depending on what are you looking for, I recommend you to extend your stay at Yellowstone NP. It's the place that has more to offer.

hi frederico.
I live by yellowstone in the summer/winter and in toscana in the fall/spring. My one thought is that the weather will be cooling so you might wsnt to go to the park first. There is a flight from paris to salt lake that is great. Maybe you could fly I into there and fly out off seattle.

Some beautiful parts of the northwest are. Teton and yellowstone parks,couer d alene, glacier, around seattle, the oregon coast is also wonderful. Alleasy to drive,

Yes, you should be aware that Yellowstone and Glacier National Parks are at high altitude and autumn/winter arrives much sooner than at lower elevations. Some roads may be closed or have limited hours.

With two weeks you might consider an alternative route - drive from Seattle down to San Francisco via the coast, then return via Crater Lake in Oregon and the Columbia River Gorge (near Portland) - easily doable in the same time, but with a lower chance of poor weather. You'd still get superb scenery - coast, the Redwood forests, mountains and "old west."

One way to avoid some driving through some uninteresting country in eastern Washington or eastern Oregon would be to take the Amtrak Empire Builder train from Seattle to Whitefish Montana. Rent your car there to see Glacier, Yellowstone etc.
When you come back to Whitefish to turn your car in, take the Empire Builder to Portland Oregon if you want to drive down the coast to Newport. The train splits in the middle of the night in Spokane. This avoids a drop off fee for returning a car at a different place than where you rented it. On the return to Portland you get a good view of the Columbia Gorge in the last hour into Portland. Check Amtrak.com
In any event, check the weather in the morning before heading out for a drive.

Yellowstone starts to close facilities in late September - October because of snow & bad weather. http://www.nps.gov/yell/planyourvisit/open_closedates.htm I'd go as early in October as you can or try and come in September. September is really nice time to visit.

Utahtea

wow......thanx every1!!!i cant believe that i have already 5 replies!!!great!!!thanx a lot!!!i'm gonna check out all the links u suggest me.....u all r great!!!

consider gardyloo's idea.

One of these days........take another trip and consider Yellowstone in Winter. You go everywhere by snowmobile or sno-coach and the scenery is fabulous. The wildlife is easier to see, too.

Bobmrg,

Winter in Yellowstone is a dream vacation wish of mine! I'd love to go, but there is only a certain time that facilities are open for winter activities.

Utahtea