'The West' was a dominant and ubiquitous aspect of Old Earth Terragen culture, especially in the Industrial and Information ages.
While the roots of Western culture go back to the classical period of Western Eurasia, the West in its full glory - as a colonial, cultural, religious, political, economic and military imperialist collection of originally European powers did not develop until the Age of Exploration, gaining ground during the colonial period of the Industrial Age, and finally attaining cultural hegemonic superiority during the Information Age. Thereafter all of the major cultural and political powers on Old Earth and in Solsys generally were either overtly Western or strongly modified by the impact of the Western memeplex. Central to the original version of Western civilization was a reasonable albeit flawed and limited democratic system and freedom of speech and information, a high standard of living, a superior technological development (relative to contemporary cultures), a Christian-secular memeticity, and a highly developed capitalistic consumer economic system. Though they might reject one or more of these aspects, from the Information Age onwards all the major cultures and polities was strongly modified by Western thought and had adopted one or several key aspects of it even if in some cases they were strongly opposed to or indifferent to Westernism and the cultures and polities that had given rise to it.
The downfall of Westernism began just as its victory seemed certain, for at the same time that Western humans had conquered eir fellows (more memetically than militarily) the first AIs were emerging and developing their own society and network. Even before the Technocalypse, Western civilization was doomed, being subverted by the early hyperturings in the same way that they themselves had subverted rival civilizations. Nevertheless, the West has left us a number of endearing legacies, including capitalism, the scientific method, freedom of information access, the Anglic family of languages, the Universal Church and other Christian or post-Christian religions, and the megacorporation.