This is a fun question. I think to get to an internetless computerized world, you have to imagine a world where mail doesn't exist, which is a very difficult scenario because you have to get to a place where an industrialized, electrified information-age economy is established without anybody writing something down and sending it via courier. There might be room for a voice-only internet if we skip letter-writing/telegrams and go straight to the telephone, but that's also tough to imagine.

I think there are worlds where the internet is never commercialized, and we wind up with a future where access is much more constrained, but that requires a very different USA, and a very different DARPA, or some other geopolitical reconfiguration. I don't know about the specific ideology that lead to the opening up of the internet in the USA, but if it never standardized, it's possible that some of those early internet conglomerates could have relied on their proprietary protocols to create entirely separate IBM, AT&T, etc. networks.