Please define "traitors" and "colonized". London is a very multicultural and cosmopolitan city. 40% of Londoners were born outside the UK.
It's still very much British though. English is the language of daily life everywhere. British law still applies everywhere and English is the de facto language everywhere even though 300 languages are spoken in London (800 in New York, apparently – one of the most linguistically diverse places on earth, along with Papua New Guinea). The UK government is still in charge. In actual colonies, it's different. London hasn't been annexed by China or Russia quite yet. Although their billionaires have bought up a ton of property.
Also, London is not the whole UK. Might as well be its own microstate (some of them actually wanted that lol, and with 9 million people and a huge economy it could be quite a successful country). Go even 1 hour away and it's a different planet (by car, that is – might take a bit longer on public transport lol). The difference is striking.
Criminals will often use whatever they have at their disposal, yes. But the fact guns are so hard to get hold of makes a big difference. Unless you're the Hulk with Matrix reflexes, there's only so many people you can physically kill with a knife or machete before you get taken down.
But give a skinny weed with a vendetta an automatic weapon and see the difference. Mass shootings are common in the US. They're almost unheard of in Europe and I don't think most people worry about being killed in a shooting. It's just not a thing. And when it is, it's huge news and remembered for years.
And yet you cling to the Second Amendment like it's Gospel, because you believe it keeps you safe and free.
This is a huge cultural difference between Europe and the US.
In the US, everyone having access to guns = freedom from tyranny and it's baked into your cultural mentality and Constitution. In Europe and other countries, *not* allowing everyone to have access to guns = freedom. Europeans feel safer precisely because they know most people *don't* have access to extremely lethal weapons and only specially trained police officers, soldiers and members of gun clubs and so on are able to own a gun (after careful vetting). I think this is a cultural difference that both sides may never agree on. But I know which one I prefer.