According to this bar chart on wealth distribution in the EU [1] there is a huge difference between the average and median wages in Germany, so I would expect the group of poor workers to be much larger than we think it is.
Of course, being poor in Germany might mean something different than in the US, since we still have better access to healthcare (at least in my opinion, I don't know enough about the US system to be 100% sure).
[1]: http://media0.faz.net/ppmedia/aktuell/wirtschaft/831437975/1...
\EDIT: I should have cited the source accurately, the chart comes from the FAZ, a huge and respected German newspaper.