And because US law enforcement have been using the private sector to bypass the need for a warrant.

I don't really know the legal arguments that make surveillance of public places into searches, but let's assume they exist and are valid... I still don't think people would be that mad about it if you thought you could trust your police to use the information half-way responsibly.

The state song of Tennessee has a line about murdering two federal agents searching for a moonshine operation. Americans only like cops if they are brutalizing minorities or striking workers.

And the ones that do have a load of training and physiological tests

The entire basis of policing in the two countries is different. This is reflected in their attitude and use of force, which is relevant when evaluating any new police power or tool.