Borough Boys have been around 2007 - so there was definitely nothing going on with them in the 70's
To address your OP. Hooligans/Firms seem to have only been around since the 70's having originated (somewhat) in Liverpool. With this in mind I would find it very hard to believe there was an emergence of hooliganism here in the states for the Cosmos or anyone.
From the WIKI page on Football Hooliganism
"United States and Canada
While soccer is traditionally viewed as a family-friendly event, violence does occur. On July 20, 2008, in a friendly match between Major League Soccer side Columbus Crew and English Premier League club West Ham United, in Columbus, Ohio, a fight broke out between rival fans. Police estimated more than 100 people were involved. An unruly encounter occurred between Toronto FC fans in 2009, upset from a loss in the Trillium Cup, and Columbus Crew fans. One Toronto fan was tasered by Columbus police.
That same weekend, a riot was narrowly avoided at a packed Giants Stadium as members of the New York Red Bulls supporters club, Empire Supporters Club (ESC), and members of the New Jersey Sports and Exposition Authority security force clashed over what the ESC claimed was unfair and repeated mistreatment. Clashes also took place in the parking area around the stadium after the game, involving already ejected-for-life North Jersey Firm (NJF) members, and the New Jersey State Police were called to quell the situation. There were several arrests, mostly of known NJF hooligans. A rare moment of violence broke out in Seattle in March 2010 after a pre-season Portland Timbers win in Seattle, when three Sounders fans assaulted a Timbers fan, choking and dragging him with his team scarf. On April 21, 2013 in Portland, a Portland Timbers supporter was assaulted by a group of San Jose Earthquakes supporters. While he was sitting in his car, he had taunted his scarf at a group of San Jose Supporters, one of which ran toward him and attacked him through his car window, breaking his car windshield and assaulting him. San Jose's 1906 Ultras were subsequently banned by the club from traveling to away matches. After much debate, the ban was lifted."