The NSA spied on French private companies according to Wikileaks docs from 2015. [1]

There's many such cases. They're well known for spying on Siemens as well. With allies like the United States, who needs enemies?

[1] https://www.spiegel.de/politik/ausland/wikileaks-enthuellung...

Linus Torvalds claims the NSA reached out to him with a backdoor

Also remember the Google sniffing?

https://www.theregister.com/2013/11/07/google_engineers_slam...

When it suits them (i.e. when there is data to be gained). But it's more often done through the courts, and when it needs to be a covert op, I'm guessing they'd get their buddies in friendly countries to do the dirty work.

If the usa does I don't understand why you expect we'd know about it. Also the us totally does and we do know about it - the nsa buys zero days - it's not exactly a secret lol