well here my 2 bob's worth.
We travel Europe 4 times a year but we have our Caravan on the back and this year it will be on the back of our X5
However travelling from the USA I reckon what I would do is try and see as much of Europe as I could and the best way to do that is by train.
Buy yourself a Europe train ticket that will take anywhere in Europe. I would plan where I want to stay in various countrys take a train to that place and rent a car tour that area and then move on by train to next place rent a car tour that area (get the idea).
You could get on the Train at Holland and travel all the way to Russia if you wanted to.
Koblenz in Germany it a lovely place to stay and not to far from the ring. Austria visit vienna and for the mountains Tirol and don't forget to try a jager schnitzel. Italy the lakes are lovely Venice is aswell almost anywhere In Italy is lovely but then it's my fav place to visit. Go to Switzerland you've got the Eiger, Jungfrau (Interlaken) and see it by helicopter
also in Switzerland every second shop is a watch shop.
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Holland well I like staying at Wassenaar which is just outside Den Hagg (the hague) and about 25 mins from Amsterdam. There are alot of American stay in this area.
Also don't forget France the area I would go to Monaco, Antibes,Nice what a lovely part of the country. You could visit Pairs but only for the day. However be aware France is the worst place for them willing to speak English every other part or Europe I have never had a problem. To finish you could sail over to Scotland and share a wee dram of Highland Park with us.