If you think USA has mass surveillance you haven't been to Asia (South Korea, Taiwan, China, Singapore, Etc).
I can drive down highways in most cities in the USA without my license plate being read (Flock isn't on highways). Also Flock as integrated mostly just records license plates. It's not recording video 24/7.
I actually touched on this in another comment below yours, using Asia as a specific example. Our crime rates are also much higher than those countries.
But while our surveillance is not as widespread as other developed nations, it is still quite commonplace. There are cameras everywhere and recording license plates seems like such a tiny and justifiable expansion.
People in the US also get angry at speed cameras or red light cameras, yet I personally think both are very rational things to want in busy areas!