Perhaps Cellar isn't focusing on Firefox anymore - the extension no longer functions, it has been updated in May of this year apparently, but no apparent improvements to functionality has been seen from it.

not working

Like other said, used to work, not anymore.... So basically useless.

Worked great while it worked. But for a while now it doesn't load any of the seller's country of origin flags at all. Amazon must have changed something that broke its functionality. I hope it gets fixed, because I like trying to buy U.S. whenever possible.

definitely a great idea and implementation is a good beginning, sadly i have to disable it currently because it prevents me from going beyond page 1

Good start with the program, I look forward to its development. Sadly you have to rely on sellers to be honest with their location, not much you can really do about that without manual modification which just isnt viable yet. Its slowish to load but loads the first 10 results relatively quickly and then takes longer to load the rest.

This is a good start. The flaw is you depend on the seller being honest in their profile. I have bought items from people who claim to be USA and the item took months from China. Still, this is a good start.