The same was/is happening in our federal system in Germany, too, within a few decades. In 1950, 20% of all bills needed the approval of the Bundesrat (comparable to Senate), because they affected the states (somehow). In 2000, it was 65% of all bills! That shows how much power the federal stage got. But we - fortunately - can (and will in this case) change the constitution, because a better division of the powers of the states and Berlin makes decisions more transparent.
I'm glad you're from Germany, since you have a firm grasp of what a federal system should look like. You also know that national governments are always trying to grab more power.