How many legislature members who are not members of any party in the USA compared to the USSR?
This page indicates that there are currently two members of the Senate who are neither Republican or Democrat, and zero members of the House of Representatives. As far as I can tell neither is a member of any party.
For most of its life only communist candidates were elected to the various soviets of the USSR.
In the Soviet Union elections (up until the Perestroika) there were only two options:
- Communists and non-partisans, running as a single block ("блок коммунистов и беспартийных")
- Against all
So there wasn't any real competition between members of the Communist party and other candidates. Each district only had one candidate pre-selected by the ruling party and voting "against all" was challenging because it required you to openly cross out the candidate's name, instead of simply placing your ballot in the ballot box. This means that essentially the word "non-partisan" is meaningless when it comes to the Soviet parliament.
Now, one might attempt to argue that the American Congress is similar to the Soviet system as 99% of its members belong to one or two of the ruling parties. However the biggest difference is that the central party committees in Washington don't hold complete control over the selection of candidates, as evidenced by the recent special election in Alabama. An even bigger example is the election of Donald Trump to Presidency, as he wasn't endorsed by many of the Republican leaders. The comparison you're trying to make is misguided, even though I agree that the American system deserves a lot of criticism.