Was the u. s. expansion, during the 1800’s justified? (the expansion of texas, louisiana, and oregon)

Yes, Louisiana Purchase allowed for it

Hope this will !

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.