The "US only" item location filter selects items that are listed as being in the United States; however, as you may have seen, not every seller that lists items in the US ships from the US as they should. You can report such sellers for item location misrepresentation, but until eBay actually cracks down, your best course of action is to avoid such sellers entirely.
Before ordering you should check the estimated delivery dates -- that is usually a good indication of how far away items actually ship from. Also, going to a seller's profile page or feedback page will tell you where the seller's account was registered. If a seller is registered overseas, that raises the likelihood of an item shipping from outside the US, particularly for multiple quantity commodity items. Checking seller feedback will often reveal if there are problems with long shipping times, canceled orders or other supply chain warning signs.
