If you have set up iOS devices to sync your calendars, but you are not seeing all of the calendars typically listed in the browser view of your Google Calendar, you can edit and add additional calendars to sync across your devices. To control which calendars will show up on your iPhone or iPad beyond the ones you "own", then you may need to log into any Google service (such as Gmail or Calendar) and visit this page https://calendar.google.com/calendar/syncselect.
This feature is documented at: https://support.google.com/calendar/answer/99358. Look under "Change which calendars get synced" and then "Sync other calendars" for detailed instructions.
You will be presented with a list of calendars in three categories:
- My Calendars (the calendars that you "own" that show up under the "My Calendars" list on the left side of Google Calendar)
- Shared Calendars (the calendars that others have shared with you, or to which you are subscribed through a URL)
- Not available for syncing (calendars for which you only have free/busy access)
Check the box next to the calendars you'd like to see on your iOS device, then click "Save" at the bottom of the window.