> Canada and Australia never had a similar problem.

Greetings from Canada. I live in Montreal. We have more of a Mafia problem nowadays than New York (no RICO here), and we were comparable in the 1930s. Bootleggers, remember? Where do you think they were running the booze from? Same "market", same mob. Yeah, they managed to dominate everybody else. That's what I mean about "niches". In fact they did it worldwide, and according to Wikipedia they're prominent in Australia, too. These are transnational groups. The Mafia is also big in Sicily. Are you going to say that's because of (checks notes) Sicilian immigration? Specifically because of a huge wave around 1900?

We also have Hell's Angels here. Ethnically "white". No immigrant identification whatsoever, totally acculturated... although I assume some of them moved here from the US. Pretty racist and anti-immigrant, actually. Cool fact: I used to live two houses away from Sonny Barger in beautiful Oakland, California. OK, it wasn't actually that cool. Those guys were really noisy. But I assure you they did not come through Ellis Island.

Apparently Winnipeg has First Nations gangs (Indians to you). Kinda the opposite of immigrants.

... plus a grab bag of others, some of them organized by immigrants. Yes, organized crime tends to segregate itself ethnically, so if one group gets the upper hand, you're likely to see its ethnicity as the face of the problem. But all ethnicities get to play, and they will expand into any available vacuum. If you hadn't had the Italian Mafia (worldwide), you'd have had something else (at least regionally).

And it's not always ethnic. Apparently there's a gang in BC that actually calls itself the United Nations.

> Tammany Hall was not a political machine in 1789.

It sure was by 1854, eh, according to your own quote? That was 38 years before Ellis Island opened. Before the specific wave of immigration that you're claiming caused the problem. Goalposts. You are moving them.

> Irish domination of Chicago's political machine long outlasted the Ellis Island era

... and preceded it. Your own link says "Of the 28 most influential Chicago aldermen of the 1890s, 24 were Irish.". I don't think they teleported from Ellis Island and took over in under 8 years.