A visible difference between the histories of European and (U.S.) American Marxism: The predominant institutions to shape and propagate the former have been political parties, trade unions, and in moments of rebellion against the bureaucratization of the first two, collectives. The predominant institutions of the latter have been the academic circle, the sect, and the cult.
This difference is conditioned in part by the differences in mainstream political and civic life between the two continents. U.S. political parties are not membership organizations with defined programs. They are not the means of ideological mobilization, but the ends. A rigid caste delimitation is maintained between the ideologist and the ideologized, so ideas are formed in more delimited elite circles: the think tank, the secret society, the religious denomination.
There have thus been two dominant trends in attempts to Americanize Marxism. One is to ape the methods of elite political formation--to attempt to turn the academic circle into the think tank; the cult into a secularized secret society; to capture the ballot line. The results are Marxisms unrecognizable as such when measured by the notions of a European orthodoxy. The other has been to attempt to Europeanize American political culture: to build a mass political party as such (the Socialist Labor Party and Socialist Party of the 1900s and 1910s; the pre-Popular Front Communist Party; arguably, the Black Panther Party as well); to revolutionize the trade union (first as tragedy: the IWW; then as farce: the more syndicalist formations within American Trotskyism); or to re-create an ideological collective on a European model (the Johnson-Forrest Tendency in the 1950s; the Sojourner Truth Organization and various Maoist formations in the 1970s). State repression has played an inarguable role in the decline of these attempts, especially of the first two types, but this does not negate the fact that all such attempts have degenerated into the forms proper to American Marxism: the circle, the sect, or the cult.