What products and applications are mature abroad, but not at home?

There are many high-end foreign portals that are not available in China. China only has the Internet system in China, but there is no website that can contact many foreign countries like Facebook. It is unheard of in China to manage the portal of billions of people like Uncle Face, which is also caused by the development status of China. China's culture is very different from that of the west, so it needs huge scientific and technological support and huge communication network to have such a huge system.