Atleast, in china, there is none of this advertising BS.
In my mind, the novel problem here is that the Chinese government can use such information in order to socially police people that nominally aren't under their control. Google in Europe or America has no desire other than to collect info for commercial purposes, and there is no inherent desire to turn over private information to any government.
WeChat in America constitutes a potential extension of Chinese governmental control onto American citizens. This can be something as innocuous and reasonable as the denial of visas due to certain communications, or something worse. American citizens may get their Chinese friends and relatives in trouble for something they say. A few cases of these, and suddenly half the American WeChat user base knows they have to watch what they say unless they don't care about people they know. Moving out of the platform is not an option due to network effects.
China has long maintained that foreign tech services offer an opportunity for foreign countries to subvert their information controls, and has banned thousands of domains and companies under the guise of protection from foreign influence, commercial or gubernatorial. What's to say that China won't turn around and do the same thing to other countries?
To your point about no advertising BS in China, well you'd be right if it were 20 years ago. Unfortunately, advertising has become a booming industry in China. Take a walk in most significant Chinese cities, and you'll find the constant bombardment of information to be more garish than any American counterpart. The Chinese Internet is no different.
Or simply border control agents asking for social media credentials, partly based on knowing you have an account?
I'm not saying I would enjoy being spied on by the Chinese government in particular... But it's not as if the "Western Internet" is free.
Finally, I think it is rather naive to think that the controlling interests behind global corporations are somehow so much more benevolent and disinterested in maintaining power, than governments are.
The cellphone meta data issue is complicated by the fact that the telecommunications infrastructure of the US is not private and only recently regulated. New industries with antiquated interpretations of law are bound to be abused by those anxious to expand their power, but I trust that the American civic process will overturn such abuses of power within a reasonable time frame. Rome was not built within a day.
Border controls are also a separate issue - it is our current understanding that the federal government has both the power and mandate to exercise significant controls at the border, and several rights outlined within the Constitution are not exercisable at border crossings. Furthermore, American citizens can never be denied entry, only delayed, so citizens can always deny information requests. Stupid usages of our interpretation of the Constitution, such as asking for access to social media accounts or electronic devices, are technically legal. But social media information have no expectation of privacy, and again access to accounts and devices can always be denied. Recent efforts by advocacy groups are also seeking to overturn this overreach of power by some foolish officials within the CBP. Another case of the law not catching up with technology.
To the point of global corporations, I'm not saying that they are benevolent or disinterested in maintaining power. Nor am I suggesting that American companies do not turn over information to the government, or misuse the information they collect. But they are private bodies. Just as citizens can perform crimes and ethically bankrupt actions, so can companies. But they don't adhere to an overarching ideology, nor do they claim to represent the will of a people. Google mucking around in America and Europe alike may be tolerated, or punished. Tencent and WeChat is different because of their entanglement with the Chinese government, and should be treated differently.
Overall, if America begins to halt Chinese influence on American citizens, and China continues to do so for its own citizens, there is at least some degree of "protection" of individual rights. This would be the foundation for protection of individual rights between any government and any individual.
So fb messenger has no expectation of privacy, but wechat does?
WeChat working in the US is like UnionPay working in the US. Ya, its great if you are a Chinese tourist or an expat with a Chinese bank account, but it is irrelevant if you aren't, UnionPay isn't going to start taking over the American ATM card market.
Before someone asks, the approximate equivalent of WeChat in Taiwan is Line. Don't know what it is in HK.
What's mildly disturbing is that many Chinese Americans, both American citizens and not, living in the US use WeChat. They use it because of their cultural and social ties with China. Chinese tourists as well have had increasingly better integration inside the US as well, which would only serve to spread the usage of WeChat to anyone who interacts with Chinese tourists. Tencent is slowly but surely gaining a foothold inside the United States as they roll out more features abroad that made it popular in China.
Are they suspect to these controls as well, despite not being within China? More importantly, whats the legal status of a Chinese corporation with the capability of invading its users privacy under Chinese law, if some users are neither not in China or not Chinese citizens?