Hi Asher,
Ed's right... I have a USB Flash Drive that I needed to be able to use between my Mac and my PC at work, and needed to format it as FAT in order for it to work. When I named the drive during the formatting process, I used a mixed case, but upon formatting, it changed to all uppercase.
If you only need it for your Mac, I would reformat it as Ed suggests - but backup the info on it first! Reformatting will erase everything on it.