Yes, the red/blue divide is essentially accurate and using it doesn't create the divide, which is already there. The only real simplification is that it's more like a spectrum rather than a hard cut, but it's still a single dimension variable (there is less complexity to it than lots of people like to believe).

The best explanation for what it truly is and why it occurs throughout history is in "Conflict of Visions" by Thomas Sowell. I'll give a précis of the argument here:

The red/blue divide is ultimately a disagreement over the span of human nature. All humans develop intuitive beliefs about human nature merely through the act of living, so nobody is actually neutral or truly 'centrist' - people who appear to be are usually just people who haven't been in a situation where the differences actually matter. But if they were to be, suddenly you'd find they picked a side.

The "free speech" side believe that human nature is limited and relatively static. Humans are corruptible, always have been and always will be. They can't perceive or handle the true complexities of reality, never could and never will. Because human nature is flawed and unchanging, there will always be war, there will always be unfairness, there will always be a divide between the rich and poor and so on. Progress is an endless struggle to find incrementally better tradeoffs, but attempting to make one thing better over here frequently makes something worse over there, and our limited abilities mean it's easy to think you found a better tradeoff when really it was worse. Attempting to change any of these things is naive, futile and usually dangerous.

The "safe speech" side believe that human nature is essentially unlimited and relatively flexible. Humans may be imperfect but they can improve or be improved over time and in the long run are perfectible. This process of improvement occurs through debate, thought, learning and reflection. Intelligence and expertise are paramount, so the best outcomes come from putting decisions in the hands of the best people. That's an important point: because the span of human nature is very wide, some people are much further along the path of enlightenment than other people are, and it's important that the less developed people don't get too much influence in society.

Almost all left/right/red/blue/free-speech/safe-speech/conservative/liberal disputes in life flow from this disagreement over one thing.

With respect to Twitter, we can see the following ideas at work:

- Safe speech side: Ideas are important, spread easily and most people are easily influenced by them. Therefore speech can be dangerous because the mere act of someone speaking can significantly damage the human nature of the listeners, making them literally worse people. Speech control is thus highly important and a moral imperative; free speech by "bad people" can seriously damage civilisation itself. The best way to stop bad ideas spreading from bad people to the lumpen proletariant is moderation by better people, who can use a variety of speech-limiting tools to ensure the best ideas win.

- Free speech side: Ideas are pretty harmless, because people are robust and can easily reject bad ideas that other people talk about. Free speech is essential because nobody has the big picture, all we have are small fragments, and because power corrupts so being able to speak out against power is fundamental. Speech controls and moderation are themselves a form of power which will corrupt the moderators, so it's better to have no controls at all and put up with some level of abuse and spam than submit a free speaking place to the tyrannical will of a handful of self-proclaimed moral overlords.

This is not a US specific thing of course. I don't know why anyone thinks that. You can see it everywhere. For instance, in Europe the EU is essentially controlled by "safe speech" types. This can be seen most visibly in the reaction of the various EU leaders to Brexit. Martin Schulz who was at the time an important figure in the EU Parliament (and went on to be briefly important in German politics), said this:

For decades the UK tabloids have performed mass brainwashing, and the leave campaign force-fed their readers with intolerance of foreigners. No change to the EU will convince those who have fallen victim to these factors. A bonfire of the EU is therefore not the way forwards.

The safe speech / perfectible-human ideas are everywhere in this short quote. People are easily "brainwashed" by ideas that they would naturally reject, except they were "force fed" them and have become "victims" - Schulz believes that people are reprogrammable biological FPGAs whose political beliefs are entirely controlled by those who speak loudly and frequently. These sorts of people also have frequently referred to dislike of the EU as a "virus" that's "spreading". Because people's views are entirely created by listening to charismatic speakers, there is little point in actually changing how anything is really done.

It is impossible for people with such wildly different takes on human nature to co-exist in the same space. If a new space was created by people with free speech mentality, the safe-speechers will not rest until they have taken it over and imposed speech controls on it, because they feel that to not do this is literally dangerous. Hence their name!