Regardless of whether or not the AVCHD folder shows as a QuickTime icon, you can import the video content from the camera using the iMovie software as you normally would.
The QuickTime Player also can be used with AVCHD files if you want. See the Apple support website at http://support.apple.com/kb/HT5409 for further information.
NOTE: Below the QuickTime icon it will display what kind of content the folder contains. In the example above, AVCHD Content is shown.