If there were collisions, I think they were probably accidents. For one, deliberate collisions would risk the loss of the American submarine too. They weren't built for ramming.

Secondly, the circumstance of an accidental collision seems very believable. Such collisions would not have been freak accidental encounters; the main mission of US attack subs at the time was to tail Soviet ballistic missile subs very closely and not be detected. The Soviet submarine commanders had some inkling of this, and responded by making erratic maneuvers to "clear their baffles" (essentially, look behind themselves, where their sonar was otherwise blind.) Trailing an unpredictable submarine very close is inherently risky. I think the blame falls on the circumstance of the Cold War itself, which compelled both sides to believe their actions were necessary.