Should I do a second PhD in Canada or the US? I am three years into a PhD in Germany in an interdisciplinary social sciences field (Global Integration/Global Studies), but I am quite disillusioned with the faculty and the quality of guidance here. Moreover, the academic job prospects are not very good after the PhD, and any other job, given EU regulations, is hard to get (I am non EU). Going back to my country, given the corruption in academics, is also not an option. I am thinking of dropping this, and applying for PhDs in Canada or the US.

Is this a good option? I would apply for single discipline such as political science. I am thinking of international business too, because my work is a policy relevant field.
As a general rule, if your current degree program is not serving your needs/goals, then yes, you absolutely should look for other options.  Hopefully the research experience you've gained in your current program will prove helpful in the future.

That said, you need to be careful in applying to a new program.  A PhD application from a student already in a PhD program raises a red flag, especially if they are already fairly far into the program.  Obviously the current program isn't working out for the student, but does that indicate a problem with the student (uh-oh), a problem with their advisor (but then why not change advisors?), a problem with the program as a whole (but then do we really want a student that was admitted to a dysfunctional program?), or something else?  And even if there isn't a problem, why should we give a slot to someone who already has one elsewhere, instead of giving a new student a chance?

The best way to ameliorate these concerns, in my experience, is to get strong and supportive recommendation letters from the faculty in your current department.  You also need to tell a convincing and positive story about why you want to move (for example: a shift in research interests that does not match the strengths of your current program).  One thing you absolutely cannot write is "I want to move because my current program just isn't good enough."