Anybody who has grown up in the United States likely knows that almost all US flags whether they be in commercial, military, or educational stances are accompianied by another flag or two. In most instances, the US flag is accompanied by the state flag and a POW flag. If there is no state flag, the US flag is still usually accompanied by a POW flag.
I went through the world of Fallout 4 and placed many flags in places that I thought would have flags in real life, such as police stations and schools. In places that already had flags like forts and military outposts, I put the POW flag and state flag by the US flag depending on the organization (i.e., a U.S. Army only structure won’t have the state flag but a Massachusetts National Guard structure will).
I also added 2 more flags that I felt were only left out because they are somewhat niche; you can discover how to build the Norwegian flag after discovering the FMS Northern Star, and you can discover how to build the Chinese flag after completing the quest “Here There be Monsters” with the Yangzte submarine. You may notice that flags have been appropriately added to these locations as well.
Hope you enjoy! Contact me at thatvillagerguy on Discord for concerns