Would simply counting the number of bends tell you how twisty the course was?
Road America: 11
Indianapolis Speedrome: 4
1) What counts as a "bend" can be difficult to decide. For example "Beau Rivage" (#2 at Monaco) or corner #4 at Road America don't look like corners. They are just slight variations on a straight. The angle and the length of the corner should also count towards the twistiness index.
2) Monaco  looks much more than three-times more "twisty" than Indianapolis . A circle isn't really twisty at all.
3) Monaco seems more twisty than Infineon because while there are a similar number of corners Monaco is a shorter track (Monaco = 3.340Km, Infineon = 4.05km). Should we calculate a ratio of corners to track length?