When you are faced with a AVCHD file on Mac, it can be confusing on how to export the clips to separate files, but this is easy.
Open the file in Quicktime player, as shown above, then select the clip you wish to view, and it will open the selected video in Quicktime player. Then go to File->Save and the selected clip will be saved in a location of your choice. This is very simple.
This is an easy way to manage these files on a Macintosh machine. This is on MacOSX Mojave. It should work for everyone out there.