Does anyone remember what San Jose was like in 2005? If they can race there, Champ Cars can race virtually anywhere!
The bottom line is do they think they can get people to come and watch?
Champ Car and CART before it were not very good at keeping market success consistant. The most profitable races are going to be the long term successes. The first year of almost any race will be a loss.
I think the European races are either ment to try to bring more money into the series (perhaps the teams more than the series owners) in the short term rather than build something long term.
Street races can work, but not every time. They like anything else take some time to build into something that carries its own momentum. What was mentioned above about Laguna probably applies even more for street races. I think the airport model is perhaps the best one, but it's not going to work in ever case either.