Hey there, jamesgriff!
Thank you for posting in Apple Support Communities.
It is possible to add the event to your Google Calendar. You can do that following the steps below:
On your computer, open Apple Calendar.
In the top left corner of your screen, click Calendar > Preferences.
Click the Accounts tab.
On the left side of the Accounts tab, click Add.
Select Google > Continue.
To add your Google account information, follow the steps on the screen.
On the Accounts tab, use "Refresh Calendars" to choose how often you want Apple Calendar and Google Calendar to sync
To learn more, check out the information found here: Add Google Calendar events to Apple Calendar - Computer - Calendar Help
Kindest regards.