So I'm English as well as Canadian, and my admittedly anecdotal experience doesn't entirely fit with the idea that it's fans of the England national side specifically who are the worst.
I've been watching a great many World Cups and Euros in Vancouver at pubs and restaurants since the eighties. At first, no one knew what was going on. A lone cop would be stationed outside a small café because Canadians heard that football (or soccer, as they call it here) fans were violent. I've watched games at the Dover Arms, the Fox and Firkin, the Three Lions Café, and many more, including seeing Italy win the World Cup in '06 on Commercial Drive (Vancouver's Little Italy). At the latter, there were ultras present, all peaceful (and we were with friends who were supporting France). Over the years, with the major football tournaments as backdrop, we've partied with Brazilians, Portuguese, and a whole lot more. It's been overwhelmingly peaceful.
And I'm not naive; I was a regular on the Stretford End in the early eighties.
Anyway, as the years went by, more and more fans congregated in these places across Vancouver, and the authorities got more clued in, so by 2006, they knew to close off blocks and blocks of the Drive. But my real point here is that I've watched England with (mostly expat) England supporters for years, and I never saw any of the behaviours we're discussing here. We were drinking copious amounts of beer and were loud and raucous, and when England inevitably lost, the silence would descend and you'd see a few grown men crying in the streets, but everyone would go home peacefully.
And before anyone says they were Canadians, not really English, you heard all manner of accents: Manc, Scouse, Geordie, Cockney, etc. I'm not saying this to defend the English—there's clearly a huge problem still—but why does it not manifest itself in England fans elsewhere, in other places? Is it the country of England itself, the social issues, the weather (although Vancouver isn't a great deal better in that regard)? What is it? I'm only adding this not in defence of England but to show it doesn't have to be that way when a great number of England fans gather.