Conversation is like Double Dutch (jump rope with 2 ropes). Timing when to jump in can be difficult if you don't know the local rhythms and rules.
Conversation is fundamentally interactive. It requires response. This in turn requires a mutual understanding of conversational patterns/conventions.
Conversational patterns are highly structured and very difficult to shift. Even when you speak another language well, you probably still use your native language conversation strategies.
American conversation resembles a tennis or volleyball match. You can either serve a new idea, or aim for the ball another player just hit.You have to move quickly; someone else may get there first.
In contrast, Japanese conversation is like bowling. Everybody watches respectfully and quietly and takes turns. You are not expected to respond to the previous statement, but to aim at the conversation goals.