In the case of seatbelts - after a law change in the UK - everyone settled down to doing the thing that saves ones own (and passengers, if they wear them) lives pretty quickly. No real enforcement needed, just a few adverts pointing out how bad you'd feel if you killed your wife / child / etc. But, without that law, no-one would have done it. Now everyone except a few idiots accepts seatbelts as being sensible safety, and no-one quarrels with the law.
I'd guess that in the US (at least some states) there would be a big fuss about freedom if there were such a law.
Seatbelts are mandatory in the U.S. everywhere but New Hampshire and Washington DC. When the laws were introduced, there was some grumpling, but not much. I think because there has never been enforcement with teeth. In Georgia the fine for not wearing them is $15. The reaction to the laws was similar to what you describe in the UK. People grumbled at first but they gradually got into the habit of wearing them. Many older people never did. Or they would drive for a few blocks and then put them on . . . sometimes while in motion, as I remember.
Years ago I read a fascinating document from the 1950. I wish I could find a copy. It was about automobile safety and surviving accidents. It said something like: 'the best way to survive an accident would be to have the passengers wear seatbelts, but of course the public would never stand for that.'
Now consider wearing masks or social distancing. There is much more reason to make wearing these mandatory, because they have a much larger effect on other people's health - and also on the economy. While COVID rates stay high, one way or another, the economy will not flourish. If everyone wears masks R is lower and the measures needed to keep rates low are less severe.
Here is what I do not understand about the opposition. This is only temporary. After a vaccine is deployed, in 6 months to a year, the pandemic will probably end and we will not need masks any more. If you had to wear a mask for the rest of your life, I could understand why people are so upset, but it is only for a short time.
There was some opposition to wearing masks in 1918, but the local governments did not put up with it. They passed emergency laws fining people and even sending them to jail for not wearing masks. Society was more authoritarian back then. Indeed, it has been more authoritarian for all of U.S. and Colonial history. During the colonial period, the government would take your children away if you did not teach them how to read by age 6, or if you let them become juvenile delinquents. (See the Massachusetts Bay school law, 1642.) We are now living in the golden age of personal freedom in the U.S. We have had less government control over our lives than ever before. People imagine it is the other way around, because people are ignorant and have not read history. Or lived through it.
The thing that really floors me is the Great Barrington Declaration (https://gbdeclaration.org/) published recently that says we should give up fighting the pandemic and go with herd immunity. Here we are months -- maybe weeks! -- from getting a vaccine and these lunatics want to swamp the hospitals with sick people, kill a million or two, and leave millions more with brain damage. Why?!? It makes no sense to me.