If you're going with "true butterfly effect" (essentially what
@metalinvader665 argues), the world certainly becomes utterly and unpredictably different with a POD that early. The sheer randomness would make it impossible to say anything meaningful about how such a world would evolve-- beyond very basic stuff like "steppes are good for nomdic cultures, so we'll probably still see those there", or "there will probably be mercantile sea-faring cultures along the coasts of the Med". But that tells us nothing of the particulars. Even in completely different parts of the world, things would end up completey different from OTL if we indeed hold that butterfly wings will alter meteological events, changing peoples' lives ever so slightly. I mean... because of a storm, a guy gets to a village he was travelling two a day late, doesn't meet the woman he married in OTL... and all their descandants don't get born. They both marry other people, meaning different descendants get to created. And those ATL partners of theirs had different partners in OTL, who
also marry different people in this ATL, and so forth and so on...
Within a generation, this noticably changes the specific population and history of their community. After several thousand years? With such things happening, time and again? Even the people of uncontacted tribes will be different individuals (even if their culture is unchanged) by the time we get to the present.
Even if we stay with strict causality, however (so: America, Australia, etc. develop exactly as OTL until contact is made), the changes are still
vast. Entire civilisations that had major impacts on world history are wiped out. In many cases, we know too little about the exact culture and identity of the pre-Indo-European peoples to even say what they might have looked like, had they been allowed to continue their development, unpertubed. In many cases it isn't even exactly clear at which point the Indo-Europeans "supplanted" other cultures, or to what extent they did. For instance: the etruscans have been mentioned as pre-Indo-European. This is not a definitive fact at all. They are generally thought to derive from the Villanovan culture, which has in turn tenuously been linked to both the Urnfield culture and the Halstatt culture. (And others deny that such links exist at all.)
Regarding the Halstatt culture: that's generally seen as (proto-)Celtic. But it's also linked to the preceding Urnfield culture, which is occasionally seen as (linked to) proto-Celtic, but most often seen as pre-Indo-European altogether. Best we can guess, the Celts derive from the Halstatt culture, which evolved from the Urnfield culture, but was clearly
changed by the influence of the Indo-Europeans. At which point those changes occurred - or how they did - remains disputed. Did the Indo-European conquer? Or migrate and assimilate, simply exterying great influence via superior tech? Or did they do some combination of both? Did they merge with the indiginous population? Or did they supplant the ruling elite? And did this all happen to the Urnfiel culture, and is the Halstatt culture the result? Or did it happen later, over the course of the Halstatt culture's existence, perhaps far more gradually?
We don't know. We'll probably never know. Not for sure. And the same damn thing goes for almost every other place touched by the Indo-European migrations/expansion. All the way to India, where we don't even know who inhabited northern India before the Indo-European got there. (There's even people who maintain that the Indo-Europeans came
from there, but I consider that pseudohistorical.)
Given such vast unknowns, I am confident in saying that we cannot reasonably describe a world without Indo-Europeans
realistically. Even if other peoples, from the same general region, undergo a similar development/expansion... their basic culture would be different. And would they have the same tech? In his masterful book on the origins and migrations of the Indi-Europeans,
The Horse, the Wheel, and Language, David W. Anthony describes how the Indo-Europeans had a vast advantage in their use of horses and chariots. (To the extent that it's suspected that the idea of the centaur originally derives from pre-Info-European peoples in Greece encountering Indo-European invaders on horseback-- seeing this fearsome foe as one creature.) The exact origins of such developments are murky. Domesticated horses and the use of chariots soon spread out. Did the proto-Indo-Europeans develop this all by themselves? Or was it a product of their region, which they cunningly exploited, but which would still have arisen without them at pretty much the same time? I tend towards the former, since genetic reseaurch has shown that
all domesticated horses on the planet descend from a very small group of stallions (and possibly from just
one). Domesticating mares was possible earlier; David anthony argues that the proto-Indo-Europeans were the first to succesfully domesticate a stallion, thus allowing them to breed stallions born in domestication... from which population all domesticated horses are derived.
If that is true, and I think it is, then "no Indo-Europeans" means "no (or at least: later) domestication of the horse". It means "no (or at least: later) use of horse-chariots". This by itself has vast effects on Eurasian history, even if other peoples basically take the place of the Indo-Europeans. And it's unclear that others
would. Anthony argues that the use of horses and chariots allowed the Indo-Europeans to become so successful, and gain such plunder and other wealth, that they could - and did - sustain a rapidly expanding population. That this population could plunder and conquer on a yet greater scale, creating the basis for more wealth and population increase... which started the Indo-European expansion in the first place.
In a world without all this, I don't know what we'd see, but it's not something we'd recognise.