Denmark doesn't arm all its police, neither do Switzerland, Austria, Finland, France, Germany, the Netherlands, New Zealand, Jamaica, Australia, South Africa or Sweden.
But my point was really about having Police routinely armed with those MP5s. That's what we see most of the time, and they're remarkably indiscriminate weapons - a sort of 9mm fly spray, in effect. But when you say
We have seen several recent terrorist attacks where Police on the scene were unable to deal with the terrorist due to lack of a gun, and ended up dead/seriously injured as a result.
I can recall the officer who was stabbed in Westminster but not really any others. And the aspect that characterised all the recent attacks has been surprise. A lot of people can get killed by a vehicle before anyone can stop it or react.
When they do react, as in the most recent incident, they shot the attackers 50 odd times. The problem then is that you get no more information from them. And I do think the USA is an excellent case study as to why arming everyone - the logical extension of arming all police - is not necessarily the best idea.
I'm not sure many think of the UK as 'a bastion of decency and civilised behaviour that does not require armed police', because there are many occasions which would suggest otherwise - I agree. But the simple fact is that although Teresa May presided over the greatest cuts to the Police force in years, when she reduced the force and armed officers from a high under Labour's administration, offences didn't rise and in fact fell. What was more striking was that the number of firearm offences plummeted.
So we obviously need armed response officers, but arming all the police is not going to be effective unless you have enough police to have one on every road in every town at every minute. Which, again, is just what Daesh would like us to do. Think of the Manchester attack. How would armed police have saved anyone in that instance? No one noticed the attacker until he detonated his bomb.
Or think of the Westminster and London Bridge attacks. The heavily armed police killed them within minutes, yet by that time the damage had already been done. How would having armed police have stopped the vehicle mowing down the pedestrians?
It's very tempting and understandable to demand we arm all the police but every scrap of information we have tells us that it won't work.