We've seen this thread get derailed by a targeted attempt at claiming America is "doomed" to Fascism (with very little in the way of material analysis to back these claims up) which has distracted from an analysis of how the left can and should organize in the U.S.
So to get things back on topic: first and foremost, we should analyze how the left operates in the Modern U.S.
Generally speaking, the only "successful" radical left party I've heard of so far would have to be the Socialist Alternative--of course they're Trotskyists, but they held onto a Seattle City Council seat and are looking to expand into purchasing property to use as an actual headquarters.
Throughout most of the United States, however, Socialist parties exist as mostly micro-sects. The DSA has seen some success (at least in terms of sheer numbers) with its "party within a party" strategy, but it's extremely decentralized and mostly incoherent, divided between caucuses of SocDems, actual Socialists, and Radical Liberals. It is, however, good for getting a few progressive leftists elected to office.
Most of the other parties have some offices in major american cities, and all of them interact with the wider world of politics by showing up to protests and mass actions and trying to recruit people. None of them have seen massive success in recent years, but I think that can be due in no small part to the American economic boom and the rise of home ownership among baby boomers.
What we're seeing in the U.S. right now is a kind of "return to form" for Capitalism. Massive income inequality and wealth trickling up to the top whilst actual property ownership goes down. Recruiting among boomers is hopeless, but there can be a lot of success in working with the younger generation as many of them see no future under the current system.
Recruitment must be done outside of cookie-cutter suburbs (as they're generally the womb of the most reactionary kind of ideology) and in the real world.
Of course this will be a bit difficult as many cities quietly pass laws forbidding the use of flyers or pamphleting, thus there's a few points I feel will be important for pushing Americans left.
>Outside of official party structures, there should be a broad coalition of "guerilla" cells focused entirely on recruitment
>These cells should be no larger than 10 or so people, as stipulated by Che
>Actions should be taken such that people are made aware of leftism, but not associated with any particular party
>Mass use of flyers, pamphlets, all done anonymously
>This coalition of guerilla cells should be willing to cross ideological and party lines with the sole purpose being communication of ideas and creating independent and democratic institutions