Default item location is actually different than worldwide; default will not show some worldwide options that either take too long or that do not use standard shipping options.
If you are searching using the eBay app, it is possible to enable lockable filters and then lock your item location filter settings so that all future searches are for items listed in the US until you explicitly change the setting.
If you use a desktop browser, it is possible to create a sample search that has that item location setting, then bookmark or save the search. If you use the bookmarked or saved search as a starting point you can continue to limit your searches to items listed in the US.
There is a third party browser add-on for some common browsers (Firefox and Chrome at least) that is called "eBay item location -- my country only" that allows users to bypass eBay's default item location search setting and only provide results in the US or North America.
