Hi Procyon, yes there is a "Worldwide" search setting on Ebay. If you open up www.ebay.com and conduct a search, it brings up only items listed on Ebay.com. International sellers can opt to list or cross-list their items on the US site (ebay.com), but auctions that are not listed on the US site do not appear in the default search.
To choose the "Worldwide" option, manually conduct a search on Ebay.com, then look at the column to the left of the list of items (with bold headings). Under the sub heading "Item Location", select "Worldwide". This will bring up all auctions matching your search on all Ebay sites.
You will notice an increase in the number of auction listings found when using the "Worldwide" search function. For example, I just did a domestic versus the "Worldwide" search for "waterman fountain pen". The domestic search yielded 2549 listings and the "Worldwide search yielded 2853 listings.
I have found a lot of interesting items by doing so!