It's not out of the box and you'll do some work yourself, but it's cheap:
Raspberry Pi ($35 w/o the clear box) +
XBMC Frodo +
A little know how can make this happen easily.
The reason you may get the exact answer you're looking for is 1) All these boxes are media streamers 1st, USB is perk 2) Newer TV's likely have USB ports or at the very least an SD card slot. My TV is well aged now, but it will still accept a big SD card to watch videos off of if I wanted to. I don't, but it's there. 3) Windows Media center, Vista, and Win7, xbox360, etc... You can skip moving files off the computer and putting it on USB drives and physically moving the drive to the device you want to use it on. Media center let's you just stream that file straight to your TV over the network.
It's just vary rare with all the other viable options available where people are still using thumb drives to watch anything off of. Even phones will stream to and from the TV now. If you look at
Roku options, only the top 2 XS box even bothers with a USB port for $100. To me, you'd be better off with the $50 LT and just stream wirelessly from your computer and stop using the USB all together. I just feel you're hung up on what you're use to and not to what else is available to adapt too.