I wonder if what you have in mind is like what Germany was before it was unified. Lots of city states that essentially ally together or don't. I don't think it is a stable situation once someone gains the means to conquer by force.
At some point, a tribe has to use force.
Obviously, it hasn't been historically.
But an interesting long-term trend (across the last few centuries) is that "conquest by force" is becoming less and less effective. In the ancient world, "conquest by force" meant you got to take their land, take their food, take their livestock, and just in general take all their stuff that they worked for without you having to work for it, and this is clearly an advantageous move. If you destroyed their infrastructure, meh. It was easily replaced.
As our world becomes more and more technological, though, an increasing amount of our wealth is in people, infrastructure, and relationships. It is effectively impossible today to "conquer" a country in the conventional sense and enjoy their wealth as a result. You can force a slave to harvest wheat, but you can't force them to participate at full capacity in a software engineering role with a hundred other people. (Part of why as many people have observed, slavery was on its way out in the South whether the civil war happened or not, albeit perhaps decades later.) Militaries remain an important component of how countries relate to each other, as a chess understanding would suggest, even the threat of mass destruction is (whether we like it or not) a very big and important stick, but today the threat is military destruction... not conquest.
If we continue even farther into this direction, well... what would the effects be?
(An interesting test case for the point of view I am propounding here is China's attempts to militarily conquer Taiwan. If they do undertake it, it would be one of the most interesting such conquest attempts in a long time, because unlike the Ukraine/Crimea where I think Russia wanted the land rights more than anything else, China wants the people of Taiwan. Will the people of Taiwan just acquiesce and continue generating wealth for China to take? Or will China discover that the jewel is much less desirable than they thought? Stay tuned.)
I'll end with, please note the difference between "less and less effective" and "ineffective". Military conquest isn't necessarily ineffective. But it used to get you a much higher percentage of the "good stuff" of the conquered territory. Today, if you "conquer" a nation, but had to wipe out its entire industrial infrastructure in order to finally convince it to stop resisting you, percentage wise you've won a lot less of what there was before you started to conquer them. It's not hard to get to the point where you won less than you would have had you just taken what you put into your military effort and used it to build locally instead of destroy.
Typically, there's a kind of time dilation where things that have happened recently seem both historically normal and of a longer duration than they really are.
In the sense that any modern trend (let's say 1920-2020) isn't old enough to really compare to something that's truly long term. It's to early to say. That, and we all have to deal with Historian's Fallacy.
I also have to say that I think that most of the Earth's land surface has more value as real estate (above and below ground) than it has as some sort of tech/people stack.
I freely admit that German is less likely to invade France (or France to invade Germany or Russia or Russia or Italy for that matter) in the modern era...assuming that wars are fought for purely profit-seeking motives.