The fundamental flaw in campist arguments is that even if we accept that Russia, China, Iran, etc. are also empires and also engage in imperialism that their "imperialism" is distinctly less influential, less destructive, and less threatening to the global working class when compared to the global doom that is American & Western European hegemony.
They are very clearly not on the same playing field and so even if they were empires using the Leninist definition then supporting them against the West isn't the grave sin 'anti-campists' make it out to be. This isn't WWI where all the imperial powers are roughly equally despicable so it's entirely fair to take a more strategic route in weakening the biggest imperial power to create a power vacuum that international workers movements can use to their advantage.
If your argument doesn't make sense even while utilizing your own logic then your argument fucking sucks.