You can use the (https://github.com/LokeshBoran/google-countrywise-calendar-id/edit/main/README.md) to get list of google calenders.
This API is use to fetch calendar ID's for google calendar API's, so you can directly pass these ID's as calendarID in different google calendar API i.e. calendars, events
Method: GET
URL: https://lokeshboran.github.io/google-countrywise-calendar-id/data.json