Communism is most definitely a political system as it has an inherent system of power relations, representation of workers, ownership of the means of production by the workers themselves, and distribution of decisions among the people until the state can be dissolved. Internationalism is a huge part of communism as is real politik, historical materialism, and other political approaches.
What I don’t understand is what you mean by authoritarian? Do you mean a literal dictatorship like in Latin America? I don’t know if a single communist country that has not had better representation than the USA as far as voting goes. I guess maybe the Khmer Rouge (I don’t know anything beyond Wikipedia for that one)?