If you are using the eBay app, you can lock your filter settings if you enable Lockable Filters in the Filter customization menu. Then you should see a padlock icon next to your selected filter option; tap that padlock so it locks and turns blue to lock that filter setting for future searches until you change the filter setting again.
If you use a browser, there is no corresponding lock setting, however.
If you use a desktop browser, there is a third-party add-on available called "eBay item location -- my country only" which can allow you to bypass eBay's "default" item location and set your preferences to your country or to worldwide.
