In what ways can the national central banks (NCBs) of the Eurosystem influence the conduct of monetary policy in the euro area? Why was the Federal Reserve System set up with twelve regional Federal...

In what ways can the national central banks (NCBs) of the Eurosystem influence the conduct of monetary policy in the euro area? Why was the Federal Reserve System set up with twelve regional Federal Reserve banks rather than one central bank, as in other countries like the United Kingdom?