Actually, I don't think it is, NatashR... a duvet here in the U.S., is a bag that a comforter, especially a down filled one, is placed in to help keep the comforter clean. It's easily washable... I have found the word applying to the comforter itself, but usually, here in the U.S. it's the cover...
I thought US comforter was more like what a patchwork quilt would look like. its a type of quilted /padded throw over.
US bedding is usually better quality than ours.
Natasha - you could go on eBay USA - there are lots of comforter (bedding of all kinds including duvet covers- the sheets always give you the thread count, etc.) sellers on there - you can look and read all about them if you want to. Hope this helps.