Memory Boxes - A great way to set a goal for yourself to reduce down your items of choice. I personally bought a lovely shoe sized keepsake box that fit into a corner of my suitcase, and filled it with small personal items (concert tickets, letters, cards) that I could not bare to part with. I've been saving 'memories' like these since my childhood so I was relieved to find a condensed way to leave nothing behind.
Remember: The basics can always be bought again. The USA has access to so many brands that we in the UK are familiar with, that there really is no need to panic. Just take care of those items that are irreplaceable to you and accept that the rest will come in time, once finances allow. You may even find you rather enjoy all the shopping that follows!