Honestly, I don't care. I'm European, I mostly listen to European/Fennoscandinavian metal, I'm getting all the digipaks with bonus tracks, and all the right bands are touring here. What more could you ask for?
But from an oustider's perspective, I have a feeling that the "upper underground" scene (read: bands signed to labels like Nuclear Blast or Century Media) are growing in the states. Until recently, those bands only used to tour Europe, now they're playing the States as well, and also sell a couple of records there. To give a few examples, there's Dimmu and Lacuna Coil on Ozzfest, Arch Enemy playing way more dates in the States than in all of Europe, heck, even totally European sounding bands like Blind Guardian did a US tour for their last album with some success, I hear.
So I guess there is potential for "mainstream" metal in the States (after all, all the bands I mentioned regularly reach relatively high chart positions in Europe) - Mr Benante just shouldn't infer the status of metal in general from the status of his own band.