I'm not sure why you want it to be one way so bad, I'm just informing you that it isn't that way. Little League has lost millions of American players because of the restrictions on practices per week, not allowing teams to be formed by selection (must be drafted), etc. And I have no problem with those rules because Little League does a great job at serving communities and providing a place for any child to play baseball. It isn't elite level baseball because it shouldn't be that.
However, those and other structural limitations are not enforced on all international leagues. In some places Little League is the option for elite baseball and that's okay because one of LLI's goals is spreading and growing the game. I have zero issues or complaints about the differences, I am just letting you know what they are. In other nations there are not nearly the number of additional organized baseball options that American kids have.
But because of those realities it is 100% valid that the American teams play to an American championship. They are playing a different game (organizationally) than the international leagues. And logistically the only way to run the LLWS to a World Championship but also have a United States Championship is to have the US winner play an international winner. So that's what they do.
The funny part is that you are the one who cares way too much about who wins a baseball tournament for 12-year-olds. The reason I'm okay with that part of the setup is specifically because it isn't that important who wins the last game. If the international teams beat the US then okay.