You're describing a fairly typical fascist regime but one which had a break with the previous country whose territory it occupies. My thought then would be not to use a modify US flag but rather something that might concentrate on the ANU regime.
Yeah, that's my thoughts too.
The flag will be a new design containing an ANU ideological symbol.
Sounds about right to me. So you are saying that a modified US wouldn't be the flag, and that it would use something completely different and new then. I am not sure what the ideological symbol would be, any suggestions?