One possibility is to set up a search the way you like, then bookmark or save that search. If you use that bookmarked or saved search as the starting point for your searches, your preferences should be maintained.
If you use the eBay app, there is a setting under "Customize" in your Filter menu that allows you to lock various filters, including item location.
If you use a desktop browser, there is a third party add-on called "eBay item location -- my country only" that allows you to override eBay's "default" Item location setting and set it to a particular country or region.
Keep in mind that just because an item is listed as shipping from a location does not mean that it actually does so. Not all sellers ship from the item location listed as they should. You may want to keep a close eye on the estimated delivery date -- that is often a good indication of how far away an item is coming from. Reading seller feedback can also allow you to spot sellers that drop-ship from overseas and avoid them.
