Difference in length of study between Europe and the states? It seems like in most European countries a student has to take a 3 years B.Sc, 2 years M.Sc and then 5 years phd program while in the U.S the M.Sc is skipped but the length of the phd stays the same... 

(Specifically talking about CS, but may relate also to other fields)

Is that correct, and if so, why is that?
Your understanding of the duration of PhD programs in the US is a bit off- the average "registered time to degree" beyond the bachelors degree for PhD recipients in the US is more like 7 years.  See

[http://www.nsf.gov/statistics/infbrief/nsf06312/][1]


In recent years there have been some attempts to reduce time to degree, and the data reported in this link are more than 10 years old, but the situation hasn't changed very much in the last 10 years.