I don't have numbers or a reference to back it up, but I say without fear of being wrong, there were almost none if any tourists at all from the US in the USSR in that time frame. The few who may have been there certainly did not attend high level meetings with North Vietnamese and Soviet leaders to determine what could be done to win the war in Vietnam against the US.
Because of the issues in that time frame, having a friend from a Communist country was practically a crime. Even in the 1990s, as a member of a special submarine crew with sensitive clearances, I was not allowed to even speak with average citizens from a very long list of "threat countries". If such a person even said "hi" to me, I would have had to report it immediately to my ship's security officer so that the NIS could start a formal investigation of that individual to ascertain whether or not they were a spy.
Looking back on past events without understanding the conditions that existed at that time does not provide an accurate perspective. The Soviet Union and its satellites were very much our enemy and our two governments behaved as such. During Vietnam, as in Korea, the cold war was on the brink of going hot. American citizens did not go on vacations there on a whim like they do now. It generally took government approval of both the US and USSR for an American to go to the USSR. Bill Clinton's casual access to the Soviet Union in this time frame is as suspicious as any American visiting the USSR embassy in Mexico. If Bill had nothing to hide, why does he both lie and refuse to comment on the events that took place in that time frame?
If you don't think Bill is a habitual liar or you are willing to admit that but it doesn't bother you in the least, I am just wasting my time typing all this anyway. I can't win an argument with someone that doesn't believe that honesty and integrity are important leadership qualities or who choose to believe the viewpoint of someone who couldn't tell the truth if their life depended on it.
I don't think Bill was too much worse about honesty than the majority of other Presidents. But he was so blatantly obvious that he felt he was above even trying to appear to be a decent person. On top of that, unlike any other President, his beliefs and goals were diametrically opposed to ones this country was founded on. How does an immoral dishonest Communist coward get elected President of the United States?
Kennedy had his problems with women and organized crime, but with a little help from the press, he at least maintained an image worthy of someone with the title President of the United States. More importantly, he had shed blood defending the country from its worst enemies and died proudly serving it. His actions during the Cuban Missile Crisis should make anyone who voted for him feel proud.
When Nixon got caught lying, he didn't continue lying to the public. He did the honorable thing and resigned. Aside from Watergate, Nixon's performance as President was exemplary. No one dealt better with the Soviet Union or China. His strategy in Vietnam was outstanding, but domestic political conditions strongly influenced by the types of groups Bill supported, forced him to leave without finishing the job.
What is Bill Clinton's legacy? Can anybody name one thing he did as President that will help this country over the long run? All I will ever remember about his years is how terrible it was to be in the Navy under Bill, how he was above the law when it comes to making false testimony in a federal trial, how anyone who could witness against him died, and that his taste in women was absolutely pathetic. (If someone is going to abuse their power as President to cheat on their wife, they should at least do as well as Kennedy

)