Well it seems to me that a lot of the history of the Northeast is centered around three powers: the United States, New Jersey and Quebec. The United States, of course, attempts to secure its trading interests along the midatlantic and New English seaboard, and must balance that interest with (or, at times, against) the interests of the Court. Quebec, of course, wants more souls for the Catholic Church, and more living room for Frenchmen. Their interests are largely focused on Canada, upper New York and inland New England, but they also want to project power through coastal New England via the Maritimes. So where does Jersey come in in all of this?
From the get go, it's obvious that Jersey is going to be run by the mob. That's obvious. The mob is one of the American myths, right up there with cowboys and George Washington. Further, many have made the observation that the mafia essentially operates as a state (and vice versa), so it's no great leap to say that as government collapsed the mob would step in to fill up the vacuum. So what exactly is the extent of that?
The core of the mob, of course, is New York City and Northern Jersey. This is the core where the mob wields the most power. It is still present but less so through the tristate area as a whole - so down through southern Jersey, Long Island, Upstate New York. At its furthest extent it goes down through Delaware, up to Providence and potentially as far as Boston. There is also a very strong presence in Philly.
As the Federal Government and therefore the Federal Bureau of Investigation retreats, the Mob moves in. It quickly consolidates control over North Jersey. The rest of its range is more contentious - New York is of course, extremely diverse, with lots of institutions (both legitimate and il) to also attempt to fill the gap).
This kicks off something called the "Jersey Wars", which comes in three phases. The first phase is consolidation against competing institutions. The Mob has the benefits of not being associated with the failed federal government and, unlike competing illegitimate institutions, it has a lot more cross-over appeal, both between different crews/families and with other ethnic groups. While the Triads may be able to consolidate their control over a decaying Chinatown, they have little chance of moving beyond that. There aren't really many Chinese gangs outside of Chinatown and in the hinterlands, and they are fundamentally foreign whereas the mob not only has the aid of many different crews with shared values and idols to call upon, but generally cultural support through extensive media penetration and a strong identification with Catholicism which many will find comforting.
Ultimately, the mob is able to consolidate a very strong core in Jersey, Philly and New York south of Westchester. Families may even for a time control large swathes of Connecticut, Rhode Island and Delaware, maybe even Boston.
The second phase comes through internal division. The several families are only loosely united and often fight at a low level throughout the first phase but, when control is consolidated, things break down. Jersey descends into effectively many different, vibrant city-states, constantly competing.
The US begins to recover strength during this period and intervenes somewhat in the conflict. The Mob, in the Medieval America as now, makes a lot of its money over control over the docks, and its domination of the Midatlantic means that it is essentially the maritime power in the northeast. The US backs various families and crews to cause chaos and leverage some control. Through this method, they gain power over much of the marginal extent of the mob's domain.
The final phase of the war comes when the US is genuinely strong, and the wars with Quebec have raised the Catholic Question. Historically, the Catholics were fairly friendly and cooperative with the Non-Denominational Church, being among the more moderate of the American denominations. However as time goes on and the Nondenom Church begins to act more liek a proper church and not just a loose organization, American Catholics in some quarters grow more hostile and sympathize with the Quebeckers. While in most of the country most catholic churches have atrophied and effectively joined the Church, this is not the case in Jersey where the mob patronizes the Church heavily, and the Church has increasingly tied itself to Quebec as the only major branch of the Church within communicable distance.
The US issues an ultimatum for the Catholic Church to fold into Nondenom, which of course is rejected. The Boss of New York, with the support of the Cardinal, rallies the families to unite and fight a brutal war against the US. In the end, the Boss of Philly, with US backing, converts to Nondenom (the city's historic stature meant the Church here had already more or less integrated) and conquers Jersey for the US, while the US takes NYC and Long Island. A few concessions are made, but for the most part Catholic identity is erased.