In answering this question, you first need to think about the fact that the internet could not have been invented without many other things having been invented first. In order for the internet to have been invented in 1915, we would have to assume that computers had been invented and were widespread, that (at the very least) telephones were widespread so that internet traffic could travel along phone lines as it did early in the internet era. The presence of computers would also imply that very high-tech manufacturing techniques had been invented. In other words, we cannot simply imagine that the internet could be plopped down in 1915 without many other changes having been made first.
An answer to this question would also depend on what we assume the internet of 1915 would have looked like. One possibility is that the internet would have been available only to a small number of the elites of society. If this had been the case, the invention of the internet would have exacerbated the economic inequality of the time and would have strengthened the hold of colonial powers over their empires. This elites-only internet would have given those elites extra access to information and communications that would have put them farther ahead of the poor. It would have also increased the advantages that the European (and American) imperialists would have had over their subject peoples.
By contrast, things might have been different if the internet of 1915 was as widely available as today’s internet is. If that were the case, the early invention of the internet might have done more to change the world. If the majority of people had access to the internet, economies would have grown more quickly. Scientific advances would have come more quickly as people were more able to share information with one another. People from different colonized countries might have been able to use internet communications to form international groups dedicated to ending colonialism. This might have hastened the end of that system. I do not think that the creation of the internet would have changed the course of WWI, but it is possible that more access to the internet after the war would have prevented WWII. More access to the internet, for example, might have allowed German Jews to publicize what was being done to them by the Nazis. This might have led to greater international opposition to that evil regime.
Overall, though, it is extremely hard to imagine the impact the internet would have had because the world would have had to be very different in 1915 for the internet to even exist. A internet-ready 1915 would have looked so different from the real 1915 that it is hard to talk intelligently about how the internet would have changed our own timeline if it had been invented in 1915.