The headquarters for both major american political parties are located in: new york city philadelphia baltimore washington,
d. c.

The centralisation of American politics can in some ways be seen as a good thing, and the state system does allow for a broad degree of independent decision-making in the individual states. However you can see that centralisation in action when you consider that the headquarters for both of the main (really the ONLY) two political parties is in Washington, D.C. - the same place as the central government and many agencies.