PhD in US university after German MSc
In a typical US MS program the research component (MS thesis) represents only a small portion of the formal degree program.  For example, 6 credit hours of thesis in a 30 credit hour MS program is quite common. In practice, it's not unusual for a student to spend more than 20% of their time and effort on the thesis.  This seems to be similar to what you're describing in Germany.  It's certainly true that most MS students who are applying for PhD programs haven't yet finished their MS thesis.  However, it is helpful to have some partial results and evidence of this such as a conference poster presentation or even a submitted paper.  
US PhD programs usually have required course work in addition to the dissertation.  On average it takes students five years or more to finish PhD degrees in the physical sciences, but there typically isn't an explicit time limit for the degree program- you're finished when you've completed the requirements, however long that takes.  


Students who come in with an MS degree may be excused from some of the course work, but this will depend very much on the details of the students MS course work.  Don't be surprised if you're required to take a number of courses in subjects that you've already studied.  Over all you might be able to cut a year off of your time in the PhD program by having a previous MS degree, but don't expect that your two years of MS study will cut the duration of your PhD program by two years.  

Completing a PhD in the US often takes longer than 5 years.  A study conducted by the NSF (using data up to 2003, so a bit out of date now) showed that the average time to degree (counting only time registered as a student) after the bachelors degree was more like 7 years, with some variation between disciplines.