The FBI once classes OMG's as the third major type of organized crime in the USA, behind the traditional American mafia and the Eurasian organized crime groups. Is this claim justified (speaking strictly about the US)?

No. Absolutely not. The days of nationwide speed rings, importing B.C. Bud, hookers in every strip club, bombings, and scaring the hell out of the Mafia are mostly over for the Hells Angels and the Warlocks and Pagans (I have family in the latter two). Motorcycle gangs are always scoffed at when they claim they are not a criminal organization but that's true in many ways. They are organizations with criminals in them but they aren't criminal organizations. There are as many guys working construction busting their ass everyday as making money in drugs and guns. Most of their members are 50 and over nowadays and they haven't really tried to recruit from the younger generation. I don't think they have the same taste for the kind of violence it takes to run a dirty business in today's market.

Alot of the Pagans and Warlocks I know do trade on their notoriety by having businesses that being seen as a "tough guy" helps. I know guys with bail bondsman/bountyhunter businesses, construction businesses, gun dealers, motorcycle shops, tattoo shops, things like that. Maybe an escourt service or two. But nothing as violent as the past. Too many of them died or are doing years for that stuff so I think the old guys have passed that on to the youngsters.