Now that we have the DW12 and some great GT's by URD, perhaps it's time to get some Indycar/Tudor circuits going.
Belle Isle may not be the most entertaining circuit for TV viewiers but for spectators, it's second to none in terms of the trackside experience. It's a great place to watch a race and the Detroit Grand Prix has always been popular with locals. The circuit, though bumpy and narrow, has a nice rythym to it.
Check out Simon Pagenaud's helmet cam:
This is probably the best of the American street circuits so I think it would be a great addition to the track roster if someone would be willing to spend some time constructing it.