Sarah - I don't know about the gps and software that you're using, but google earth uses kml and kmz files. There are gpx to kml converters online. I do a lot of lat/long stuff in excel and convert to kml using csv2kml, so there a lot of options out there for you to get your travels into google earth
I just figured out a way to sort the data from Spotwalla and then sort it. I never did figure out a way to use it to calculate distances in one stop, so I just did it in Google Maps using the same data to figure it out. This is what I came up with in the end, which is good enough for (non) govt work!
-Charleston, USA to Southampton, UK: 4,300 (at sea)
-Southampton, UK to Mamaia, Romania 2,130 (included UK, France, Belgium, Netherlands, Germany, Czech Republic, Slovakia, Hungary, and Romania)
-Mamaia, Romania to Astrakhan, Russia: 1,730 (including Romania, Moldova, Ukraine, and Russia)
-Astrakhan, Russia to Semey, Kazakhstan: 3,100 (including Russia, Kazakhstan, Kyrgyzstan)
-Semey, Kazakhstan to Ulaanbaatar, Mongolia: 2,440 (including Kazkakhstan, Russia, and Mongolia)
-Ulaanbaatar, Mongolia to Vladivostok, Russia: 2,700 (including Mongolia, and Russia)
-Vladivostok, Russia to Saikiminato, Japan: 720 (at sea)
-Saikiminato, Japan to Yokohama, Japan: 750 miles
-Yokohama, Japan to Tacoma, USA: 5,000 miles (at sea)
Total on the rally miles: 9,400 miles
Total around the world thus far: 22,870 miles