You can't cherry pick a couple of examples of where extreme power grabs were curtailed and say, "See, the government is giving up power!" You're looking at local down trends in an overall upward curve and declaring the whole thing to have a negative slope.

In order to make your case, you'd need to start with the Constitution and the strict limits that it placed on the Federal government and map that to the authority it exercises today. The trend is in the opposite direction you're thinking of.