When you want to map multiple items with the same location in Fusion Table, only one item is displayed and all the others are ignored. There is several workaround to this major limitation, and the most common is to change slightly your coordinate (longitude / latitude) so your point will appear close to each other on the map (tip from the google fusion team itself).
When working with large data set, identifying and manually correcting all records sharing the same location can become time consuming. So I've been looking how to deal with this in Google refine and ends up with this straight forward process.
1. Create record based on the location sharing the same coordinate in fusion table (you can work with city, country or by creating couple long/lat). View the tutorial to create record and switch to record mode (see difference between a record and a row).