Just because there are a lot of transactions at a low level doesn't preclude the possibility of larger transactions with cash and the USD. The credit card systems, banks and all other parties can handle transactions up to enormous sizes (I am not sure if/what the limit even is) and all that happens without affecting the USD. There are other currencies I would consider toys as well used by real countries. Many of the smaller ones that don't allow you to convert them freely are basically toy currencies as well. They are models, they work in small scale, but for whatever reasons are very limited (in those cases the limitation is often governments cant handle foreign exchange and speculators). Bitcoin is a toy because it can't handle size to the extreme.
I think at this point we're just disagreeing over what constitutes a toy. I have credit cards with credit limits under $10,000, but I wouldn't consider these to be toys, even though I couldn't use them to, say, buy a house. But even though your definition seems odd, I guess I can't really say it's wrong.
