Menu links point at live store content, so deleting content affects the menus that link to it.
Before you delete
When a resource's delete confirmation reports menu impact, it shows which menus reference that resource and how many items are affected — so you know the navigation impact before you confirm.
Automatic cleanup
After the delete, the affected menu items are removed automatically, including any child items beneath them. Your store's activity log records the removal and why it happened, so a menu never keeps a dead link.