GoAround when Cleared for Visual Approach

This is a big ATC issue in the US, especially at airports with heavy traffic. A flight cleared for a visual approach requires so much less attention and separation than does a flight cleared for an instrument approach. International pilots flying into the US from abroad need to be aware of this differentiation in ATC procedures from what they may be accustomed to, in order that they are prepared to execute the correct GA procedure, all depending on the most recent clearance from approach control. While flying internationally, it was my experience that ATC and (or ATS) seldom if ever changed the approach clearance from an instrument to a visual, even after the crew reported "Runway IN SIGHT". Most often Approach Control just acknowledged the call and switched the flight to tower. But the flight clearance was still the same instrument clearance, and therefore MAP clearance was still valid. But most often this is not so in the US. It is a very important training goal for non-US airlines to familiarize their international crew members flying into the US to be aware of the clearance changeover by approach control, from an instrument approach to a visual approach and all that goes along with that clearance changeover, most especially being the ATC expectations for flight crew actions in the event they get a tower directed GA after being cleared for the visual approach. ATC does not expect that the crew will fly the MAP as published, but rather will stay with tower for either a visual integration into a VFR downwind pattern or a handover back to approach control for radar vectors back into the instrument patterns to return the flight back to final. If the crew just begins to fly the MAP without clearance, there may very well be separation issues, since the airspace for the MAP may not have been protected ahead of time. This again is the consequence of Approach Control changing the clearance to a visual approach.