Terrorism may well continue but is the level of terrorism the same or less than might otherwise be the case. A question that neither of us has the knowledge or information to answer honestly and openly.
You have proof that some terrorism continues. None of us have proof that no terrorism is stopped by monitoring - my suspicion is that there would be more terrorism if there wasn't a level of monitoring, your position is there wouldn't. Without direct access into the security services we aren't likely to get an answer.