I am not talking about typical NASCAR and IndyCar oval tracks like Bristol, Richmond, Pocono, Phoenix, … but about the most important road courses which you can find in other racing sims and games. For example some (all) tracks from the list by @fischhaltefolie : and of course: Barber Motorsports Park Lime Rock Park Portland International Raceway and some "exotic" stuff like Circuit Mont-Tremblant
While I love to see new tracks, we all do, it worth noting that many of R3E partners are European based, so Its make sense that there where the most tracks will be, but hopefully that will change as time goes on.