The US isn't the UK or China and different cultures deem different things as acceptable. The UK for example is also a monarchy, which would rial up people in the US if proposed there.
Additionally the trust that the government uses these cameras as intended is apparently higher in the UK than the trust of Americans that Flock will not misuse their surveillance technology.
In the UK overall, 64% of the population support police use of facial recognition technology to some degree and only 11% were opposed to its use [1]. The survey also looks at support for different szenarios, but overall many generally did not oppose it, while in the US 47% oppose the use of flock cameras [2].
The Flock stat is interesting because 46% of Americans believe widespread use of facial recognition would be a good thing (27% unsure).
Maybe people oppose Flock because it's not going far enough! Or maybe there is a coordinated campaign against a license plate reader for some weird reason
No, it arrests several thousands of people every year for breaches of the communications act(s) - this could be for online harassment, stalking or trying to defraud people over Facebook messenger.
Additionally the trust that the government uses these cameras as intended is apparently higher in the UK than the trust of Americans that Flock will not misuse their surveillance technology.