Though it's quite likely that Russia was involved in the Assassination of President John F Kennedy:

The Warren commission didn't want to have a nuclear war with Russia over Kennedy's assassination. So, even if Russia and Castro were directly involved it couldn't be allowed to come out that this was true that likely Russia and Castro hired the Mafia to assassinate first Kennedy and then Oswald to get rid of evidence (whether or not Oswald actually shot Kennedy or not).

The same I think is true now. I'm sure that Russia was directly involved in the rightist insurrection at the Capitol Building on January 6th where many died or were wounded. However, the government doesn't want a nuclear war with Russia over this so likely this can never come out as to just how deeply involved with this insurrection Russia actually was without sparking a nuclear conflict with Russia.