Why history of Architecture is history of nations?

In reference to the statement, history of architecture is closely related to history of nations or vice versa. Yet, one could argue that there are no element of nations-states in the definition of architecture. While this argument and debate is going on and on, i personally think that history of Architecture is related to history of nations and vice versa. One could not tell the history of architecture without relating to the history of nations. Similarly history of nations is incomplete without history of architecture. 

A very simple example would be many congress and important meetings by the politicians took place in a buildings like Parliament building or Trade Centre. In fact, the building itself is a symbol and identity of the nations. Not only that, it is also a place for people to congregate for community meetings. Take for example, the Civic Centre is a place where people gather to join in for campaigns. The Majistrate has also its distinct architecture that distinguish it from other buildings.