Regardless of whether you think House is an authoritarian tyrant, he doesn't fit the bill of imperialist IMO. Purely because he has as much of an argument of being a native power as any of the tribes do. He was born there, he has strong investment there, he has committed himself to his native land and his territorial claim does not expand beyond that. In the post-nuclear world the historical clock is set to zero and all that defines a native power is originating from there and having the power to hold influence over it. Largely because obviously the civil/legislative authority has literally been erased. To argue otherwise is to say the only legitimate government in the Wasteland would be the Enclave, and even they don't fit the bill. If House doesn't have recognition as a legitimate native power, nobody does. House ticks the boxes of both. That's without appealing to the argument that House has a stronger claim to the region considering he spared it from nuclear annihilation, which is a step above the claims of the Slither-Kin or the Boot Riders (People who were born there and held the violent power to hold it, of which House has both). To argue that the Mojave tribes have a more legitimate claim over New Vegas than House is to argue that they do so by the merit that they did something, instead of House who simply observed. By the same logic, the NCR and the Legion have about as much right since in this line of argument, native birth is irrelevant (since House is explicitly born in Las Vegas.) As Benny says (as nativist as it gets considering he's the progenitor of Indie Vegas) "Respect where it's due but the man's about as square as it gets" - the division between Indie and House Vegas is not one of a people versus an outside power but rather more simply how the people are governed. Authoritarian and repugnant do not equal imperialist.