What are you even talking about? Sakai has anti-imperial aims like every other communist and sprinkles Lenin quotes throughout his work. It is not un-marxist to believe that the United States cannot be rehabilitated. Lenin was right about the class contradictions in the US but he was objectively wrong in his optimism of the American working class given that western socialism failed where socialism in the global south didn't.

The 32nd Annual Convention of the American Federation of Labour, as the association of trade unions is called, has come to a close in Rochester. Alongside the rapidly growing Socialist Party, this association is a living relic of the past: of the old craft-union, liberal-bourgeois traditions that hang full weight over America’s working-class aristocracy.

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For, strange as it may seem, in capitalist society even the working class can carry on a bourgeois policy, if it forgets about its emancipatory aims, puts up with wage-slavery and confines itself to seeking alliances now with one bourgeois party, now with another, for the sake of imaginary “improvements” in its indentured condition.

The principal historical cause of the particular prominence and (temporary) strength of bourgeois labour policy in Britain and America is the long-standing political liberty and the exceptionally favourable conditions, in comparison with other countries, for the deep-going and widespread development of capitalism. These conditions have tended to produce within the working class an aristocracy that has trailed behind the bourgeoisie, betraying its own class.

https://www.marxists.org/archive//lenin/works/1912/dec/07.htm

Marx and Engels did not reconcile themselves to it on this ground; they exposed it. They did not forget, firstly, that the trade union organisations directly embraced a minority of the proletariat.

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Neither we nor anyone else can calculate precisely what portion of the proletariat is following and will follow the social-chauvinists and opportunists. This will be revealed only by the struggle, it will be definitely decided only by the socialist revolution. But we know for certain that the “defenders of the fatherland” in the imperialist war represent only a minority. And it is therefore our duty, if we wish to remain socialists to go down lower and deeper, to the real masses; this is the whole meaning and the whole purport of the struggle against opportunism. By exposing the fact that the opportunists and social-chauvinists are in reality betraying and selling the interests of the masses, that they are defending the temporary privileges of a minority of the workers, that they are the vehicles of bourgeois ideas and influences, that they are really allies and agents of the bourgeoisie, we teach the masses to appreciate their true political interests, to fight for socialism and for the revolution through all the long and painful vicissitudes of imperialist wars and imperialist armistices.

The only Marxist line in the world labour movement is to explain to the masses the inevitability and necessity of breaking with opportunism, to educate them for revolution by waging a relentless struggle against opportunism, to utilise the experience of the war to expose, not conceal, the utter vileness of national-liberal labour politics.

https://www.marxists.org/archive/lenin/works/1916/oct/x01.htm

Compare with Sakai, who sounds almost exactly like Lenin but with a little Gramscian twist to account for the failures of 20th century western socialism:

The Euro-Amerikan “left” has completely mystified the question of class consciousness. They see in every labor strike, in the slightest twitch for reform, examples of proletarianism. Some “socialist scholars” (a self-awarded title, to be sure) conduct almost anthropological expeditions into the settler masses, seeing in every remembered folk song or cultural nuance some profound but hidden nuggets of working class consciousness. Others, who have spent years as working class “experts,” find proletarian vision in every joke about the bosses told during coffee breaks. This is not politics, whatever else it may be.

There is nothing mystical, elusive or hidden about real working class consciousness. It is the political awareness that the exploiting class and its state must be fought, that the laboring masses of the world have unity in their need for socialism. The Red Army is class consciousness. An action for higher wages or better working conditions need not embody any real class consciousness whatsoever. Narrow self-interest is not the same as consciousness of class interests. “More for me” is not the same slogan as “liberate humanity.”

Lenin wrote on this: “Only when the individual worker realizes that he is a member of the entire working class, only when he recognizes the fact that his petty day-to-day struggle against individual employers and individual government officials is a struggle against the entire bourgeoisie and the entire government, does his struggle become a class struggle.”

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This thesis is not “anti-white” or “racialist” or “narrow nationalism.” Rather, it is the advocates of oppressor nation hegemony over all struggles of the masses that are promoting the narrowest of nationalisms — that of the U.S. settler nation. When we say that the principal characteristic of imperialism is parasitism, we are also saying that the principal characteristic of settler trade unionism is parasitism, and that the principal characteristic of settler radicalism is parasitism.

Every nation and people has its own contribution to make to the world revolution. This is true for all of us, and obviously for Euro-Amerikans as well. But this is another discussion, one that can only really take place in the context of breaking up the U.S. Empire and ending the U.S. oppressor nation.

Also to add, i havent read Sakais book, but i do know that the group that really popularized it, MIM (Maoist Internationalist Movement) were an extremely secretive Gang of 4 maoist third worldist group. They believed that USSR and Deng Xiaopings China were social imperialist, capitalist and revisionist, that the Cultural Revolution and the Gang of 4 were great, and that white americans are all exploiters and will never be proletarian (which is unmarxist bs as you already said). This group was very secretive and dissolved in 2008. There are a lot of conspiracy theories about them and J Sakai.