A remarkable thing about this action we get to see: Cloud William is not just a local boss, he's the boss of all bosses. Why, he's the one with the sacred relics!
Whether he's the boss of the local "North America" (whatever shape this continent) or an even bigger whole can be debated. But merely local he ain't.
Unless there are thousands of copies of the document and the flag, that is. We have to consider in any case how such things could survive for a thousand years if rolled up in some saddle bag. There might be a whole cottage/wigwam industry churning out hundreds of those things every year, of course, but in that case we'd expect the errors to creep into the copies and not just their verbal interpretations...
Or then the unique originals might have been made time-proof by technology more advanced than that available in our 1960s. This would in fact be a likely scenario if they were originally introduced by a John Gill style meddler traveling in a time machine and perverting local cultures into images of Earth on the verge of global conflict, for obvious personal gain as the Fuhrer or the President of the nation enraged to self-righteous world domination.
In that case specifically, and in any case, really, all bets are off as to whether the lands really are ancestral to the clueless Yangs. Since their culture hinges on misunderstood relics, it might be their ancestral lands are on a different continent altogether, and they are merely finishing an invasion job launched and botched by their ancestors. The Khom village does not exactly convince as "ancient Yankee"... Any more than it does as "ancient Communist Chinese", for that matter.
Timo Saloniemi