Legally the government can’t record you without your consent.
In public, you have no expectation of privacy - so anyone can film anyone, government or non-government. That would be most police activity. Any other police activity - such as when raiding a home - would be subject to standard legal review in terms of admission into discovery and whatnot.
With a warrant, they definitely can legally record you without your consent and your knowledge, e.g. secretly invading your home and placing recording devices there - IMHO that's the point of the parent post; while there are checks and balances that require legal review, in the end, the government can do all that unilaterally after a judge approves that it is necessary.
Yes. Not just with a warrant, but often without a warrant or just cause. The police can lie to you, violate your rights, and do almost anything they want to you, but if you don't have body cam or other video/audio evidence, as so many, many people have found, you are screwed.
There is an excellent shortcut called "Hey Siri, I'm being pulled over" that "will dim your phone, pause any music being played, and start recording video from your front-facing camera."
Not all cops are bad, but the power imbalance makes these issues necessary for citizens to protect themselves.
My point is that the same body of text (state law) that defines wiretapping laws (recording consent) also defines that the police can record without consent with a warrant and/or with probable cause - and if not, the footage (and other gathered evidence) is both inadmissible in court and could be grounds for a lawsuit depending on how egregiously they violated your rights.
Only in the US. In most developed nations, this isn't the case: even in public you have a certain amount of privacy allowed, so for instance, people aren't allowed to take your photo without permission. Of course, there's practical limits here, but usually it comes down to whether the person is the subject of the photo or not. If a person sees themselves in a public photo, but they're in a crowd off in the distance, then that's ok. If someone is following them around and taking fairly close photos of them, that's not.
In public, you have no expectation of privacy - so anyone can film anyone, government or non-government. That would be most police activity. Any other police activity - such as when raiding a home - would be subject to standard legal review in terms of admission into discovery and whatnot.