how do i delete foreign holidays that are showing up on my calendar

It appears Apple's late February response to the outcry at the removal of religious holidays (which only represented Christian events) from the calendar was to put holidays for all major religions on the calendar. Subscribe to a calendar that only has what you want.

Use iCloud calendar subscriptions - Apple Support - https://support.apple.com/HT202361

iCloud: Delete or hide an event in iCloud Calendar - https://support.apple.com/kb/PH2684?locale=en_US

How to add calendar events to your Calendar application for OS X/Mac OS and iOS - https://discussions.apple.com/docs/DOC-12741

What does "foreign holidays" mean exactly in your post?

Recently the US Holidays calendar has been expanded to include various days like Ramadan and Lunar New Year. If you don't care to see these, remove the US Holidays calendar from your list of subscribed calendars, and add those specific holidays (e.g., Independence Day) that you wish to see to your personal calendar.