In Germany it's not the job of a prosecutor to get the maximum possible sentence, so no the problem doesn't exist in the same way in Germany. If someone in Germany commits a crime that gets 3 years and another that's 4 years that doesn't simply add up to 7 years. Our system is much more well designed.

Being tough on crime happens to be a politicized topic in the US and there are many people who do hold the opinion that the US incarnates a percentage of it's population that's significantly to high. It's no Republican vs. Democratic issues but that doesn't mean it's not political in nature.

In this case I'm not sure whether blackmail is really the right term. Wikipedia defines blackmail as "Blackmail is an act, often a crime, involving unjustified threats to make a gain or cause loss to another unless a demand is met." Is using a valid law for charge inflation an unjustified thread? That depends a lot on your political beliefs.