I thought I would follow up on my comment above with a different answer that really did fix this problem for me.
The originally accepted answer has a major flaw - for me at least - these days (I don't know if it was always like this): If you add a shared google calendar that way (by accepting an invitation), it shows up in Google Calendar under "Other Calendars". When I follow that link, and then check off the calendar in question, it creates a completely new, independent calendar Window in Mac OS Calendar, under the Window menus. This window doesn't have any of my other events, and these events aren't in my main calendar.
The following procedure does get the shared calendar events to show up in my main calendar window. I'm on a Macbook Pro running Big Sur (yes, it's very old at this point):
- On the google calendar invite email, click "Add this calendar"
- Go to calendar.google.com & find the new calendar under "Other Calendars" (in the bottom right, at the time of this writing)
- Hover over it to reveal the
...
menu & click Settings (It's actually a vertical stack of three dots)
- In the Settings pane, scroll down to where it says
Public address in iCal format
- Copy that entire link (double-clicking on it selected the whole link for me)
- In Calendar on my Mac, select File -> New Calendar Subscription
- In the following pop-up, for "Where:" select "iCloud"
- Set the other options as you like & accept the dialog box (I don't remember if it was
Add
, OK
, or something else)
Now the other calendar's events appear in my main calendar window along side all my other calendars. This also caused it to appear on my iPhone with no extra work.
I suspect that it will work if you choose the other "Where" (My Mac), except that won't get it onto other Macs or iOS devices.
Note: In some of my searching, I found some leads saying that the solution is to have full ownership permissions on the shared calendar, so that it will show up in Google Calendar under your calendars instead of Other Calendars. I did not pursue this as it required coordination with someone else, and I don't know if she would have agreed to make me a full owner.