[astebbin]

Can Facebook and other US tech companies move in WeChat's direction successfully, in the West? Why did WeChat take off as such an everything-application in China? Do the same necessary motivations and trends exist elsewhere?

I'd speculate not, at least not in the US. Here, more people have different types of computers (laptops, desktops, tablets, phones, set-top boxes) which are all united mainly by Web browsers / technologies. The Web is naturally - or at least, has been historically - more open and less conducive to walled gardens. Consequently, I think US consumers are used to the experience of getting news from (for example) the Washington Post, shopping on Amazon, and checking email on GMail, while navigating between these sites without too much hassle. This experience has largely been replicated on mobile devices, at least for me, despite the best efforts of Facebook and others to keep me locked in their app outside of mobile Chrome and Safari.

Since the Chinese government won't allow strong foreign competitors to penetrate their domestic market, I have to assume that Facebook, Google, and so forth are targeting other countries with these all-in-one messaging apps. Perhaps India would most resemble China's mobile-dominated market?