The reason the US has a "liberal" position on such things as street photography goes much deeper than the problems of photographers or the concept of privacy. It goes to the whole idea of a democracy -- that if you can't know what's going on, how can you be a responsible citizen? That's why the US separates "commercial" usage from anything that could be argued is reportage or art, because art (as well as reportage, and sometimes better) also reflects what's going on in a culture. The idea of street or art photography is a logical evolution of the real intent, which is to allow reportage of political and other news events that the governing authority might wish to suppress, but which the public needs to know about (like lynchings in the American South, which might not have ever stopped without the horrifying coverage they engendered; the racist governing authorities at the time certainly had no intention of stopping them.) The American argument would be that if you draw complicated lines about what you can and cannot photograph or report upon in public places, where will the lines stop being drawn? The answer is, they won't be, when it's convenient for the governing authority to keep drawing them.
The US also makes it clear that you *can* have privacy -- nobody, including the police or the FBI, can break into your house or any other private place (like your car) without a warrant, or without knowledge of an immediate crime taking place. (The whole thing gets complicated, because if you are in your car, and you have a bag of weed laying on the front seat, and a cop stops you for a traffic offense, and sees the weed, he can arrest you and enter your car to secure it, without a warrant, because the weed is in public view. If it was in the trunk (boot) of your car, a private place, then he could not enter it.) By the same reasoning, nobody else can intrude on your privacy either, and that includes photographer. But you have to assert your privacy, and then you have to physically achieve it. You can't just raise a barbed wire fence around your property and stand behind it and say nobody can photograph you from the public street. You have to actually be out of sight.
Ultimately, I think the European system is a problem that lends support to authoritarianism. But one thing I've noticed in Europe (including the UK) is that people there seem to have a taste for authoritarianism. I think it gives them a sense of stability, which works until people start disappearing into the gulags. When Americans start disappearing into the gulags (American Indians, Japanese-Americans during World War II) at least people know about it, and there are protests, and eventually some possibility of some kind of recognition of wrong, and some possibility of compensation.)
John, you seem to be suggesting that democracy somehow began as an American idea, and that it is today its flag-bearer. Not so by many centuries, and by a long chalk. Hanging flags from every available support and waving them on every occasion does not a democracy nor a country make, though it may define one or two.
Knowing what's going on is an admirable concept, but hardly supports being a street snapper. I think there's a world of difference between a so-called street shooter doing it largely for kicks, and a news photographer doing it for information that can, in turn, be relayed to the world. I can't stretch my imagination far enough to merge the drive to street with the reporting of lynchings, a sound reason for reportage that, today, rather than please the smug mugs of the thugs that did those things (as is obvious in the photos), would instead have the photographers hanging from those southern trees too.
That contemporary street may be derived from reportage isn't difficult to understand: that's what today's street guys are trying to ape, as I already suggested: wannabe HC-B cats, every last one of 'em. That said, they may believe they are trying to be Robert Frank or even dear old Garry, but it all goes back to reportage for magazines and newspapers. I often wonder what Garry did with all that stuff: did it actually sell and pay any bills? I really have no idea. It did no favours for most of the later people until it was possible to convince the art world that hey, it's art too! and by that time many of them were dead, so it was academic at best. There is no point in trying to fill a gap that no longer exists - street today is about self and ego, not reporting because nobody's going to print your stuff in their news magazine. What news magazine?
Authoritarianism as a European taste? Don't know about that, but certainly the more intelligent voter realises that without order you have chaos, and that chaos brings no good to anyone. Very few Europeans (apart from criminals), knowing what they do today from the American example, would ever desire their laws to enable the ownership of guns by the average Joe. They see enough crime as it is. Rampant gun ownership could only increase it to an even more deadly level. Rather than being any romantic nod to democracy, I think the relative lawlessness that seems to pass as part of the American ideal is more a sign of immaturity than of sophistication. If one desires a peaceful life, then it's not difficult to understand that that same peace must be extended to the rest of the community too. Selfishness brings no harmony.
Does government seek to erode personal freedoms? There may be some that do, especially the religiously driven ones, but you don't have to go as far as to the Middle East to find that. Birth control? Abortions?
At the moment, in Britain, we seem to have a govermnent that can't make up its mind whether it wants to save lives by strict quarantine regulations, or to play to the idiots who appear to believe the pandemic is all about the common cold and influenza. Heysoos, they can't even find the moral courage to fire the architect of the distancing policy who then went on to breach it with his entire family in the most appalling way. It attempts to bring in a cellphone app to track possible infection contacts but even there, lacks the guts to make it mandatory, leaving it voluntary instead, which means, effectively, useless. That's government clamping down on civil liberties? That's government showing its weakness and dependency on slogans, unelected officials (ironic, then, that so many its followers down the Brexit trail condemned Europe for its supposed dependency on unelected mandarins!) and with no deeper concern but to be relected next time too, so nobody must be offended less a vote be lost. Not much sign of any powerful democracy killers there... more, I'd suggest, of power-hungry individuals whose sole concern for power is not governance itself, but using position both to buy influence and to slant public spending policy in order to make themselves and their shell companies richer. A pox on them all.