The EU is not like the US. The US constitution specifically states that any powers not granted to the federal government by the constitution are retained by the states or the people which, until relatively recently, meant that the federal government had very little actual power. Strictly speaking it still has very little actual power, but it has arrogated a great deal to itself following the american civil war and the subsequent war powers acts and various inter-war acts that granted it "temporary" power during the world wars. Nevertheless, the states are still able to legislate freely in all areas except foreign affairs and, to a lesser extent, military spending. They can't create legislation that interferes with inter-state commerce, but that doesn't actually prevent much. Meanwhile, federal laws become laws the moment they are signed by the president, without any froo-farah or re-implementation by the states.
In the EU, the situation is quite different. Member-states have very little sovereignty these days. Instead here there is a concept of subsidiarity: When a directive is created in a specific legislative area, that entire area becomes off-limits to member-states, except where the EU specifically allows them to continue legislating. An example is road safety. The EU has created certain directives on road safety in order to harmonise road safety practices across the entire union. The up-shot of that is that member-states are no longer allowed to legislate in that area, with the result that when, several years ago, a proposal was put forward in Parliament to require more and more visible reflective markers on trucks in the UK, it was shot down because that area of legislation was an EU competence.
Were the EU to allow member-states to exercise subsidiarity in that area, it would have included wording to that effect in the directives that had granted it competence over that area of legislation.
Also worth remembering that, unlike US federal legislation, directives (not including technical and regulatory directives) have to be implemented into law by the member-states' own legislatures, which leads to what may be politely referred to as fuck-ups, as amendments and translation issues introduce little caveats and minor but significant differences - and worth remembering, too, that each country has it's own legal system that has to be taken in to account when drafting legislation to implement a directive, which leads to some instances of law that directly conflicts with existing legislation.
Now, of course the issue is a german court, rather than the german legislature. The courts are also rather peculiar. There are no equivalents of the US federal court circuits, nor any direct equivalent of the supreme court, with the closest being the European Court of Justice (and please remember that the European Court of Human Rights is not an EU institution - something I often forget in my rantings). Member-state courts function as both "state" and "federal" courts, but there is a horrible amount of overlap due to the aforementioned subsidiarity and competence issue. If a german court were to rule on a purely german legal issue, it would have no effect outside of germany. If, however, a german court ruled on an issue that had become an EU competence, there is currently no clear measure of where that court's jurisdiction ends. Does it merely rule on the german law implementing the directive, or against the directive itself? Do directives grant german courts jurisdiction over the entire EU when ruling on that particular competence? It hasn't been decided yet
Then the issue becomes, what to do? On one side you'll have people who say "the system must be clarified, streamlined and simplified". They would favour tighter integration and harmonisation, with the EU becoming more of a unitary state. Another side would say "we need to loose, and rationalise", turning the EU into a federal model similar to the United States circa 1880, with very little power residing in the central government. A third group would say "lets call the whole thing off", desiring an admittedly messy divorce and a restoration of national sovereignty, along more holding our own politicians to account. All three would solve the issue of lack of clarity in different ways. I favour the latter, though I'd also be able to live with the second option, but whichever side of the issue you stand on it's pretty clear that the way things are at the moment is a complete and utter mess and that some clarity would go a long way.
There are other arguments too (one being that the EU is largely useless, as the majority of it's activity is to be merely a rather meddlesome middle-man between the member-states and the various ISO committees) but this post is going on far too long.