I think the low number of vacation days is just a side effect of Americans not having such a strict compartmentalization between "work" and "life". I worked on both sides of the Atlantic and although I settled in Europe now I actually like the US work ethic, the low number of vacation days notwithstanding.
For many Europeans work is something they do to have bread on the table and the "real" life is that part you're not working. For many Americans their work is their life and the free time they have gets intermingled with work (they take the kids to the company barbecue! never heard of that happening in Europe).
But if most of your waking moments are spent doing something which is not your primary objective than you could say the Europeans are the sad ones.
(Side note: I am now in the happy position that I enjoy running my own company, I might feel different if I had a lousy job)