They can definitely do all that, but the last point is a bit harder. European companies would have to be willing to produce a vehicle certified to CMVSS. They might not see it as worth it or they would definitely be charging the TTC a lot more. MAN, Volvo, Mercedes, and Scania all tried to enter the North American market in the 1970s and 1980s. However their presence was short lived after not meeting sales expectations. So I would think there is a lot of hesitation to try again.
Actually, I should add: Daimler is now selling a new Mercedes coach in North America with a design expressly for North America. So I guess there is some appetite for expansion. But this coach comes as a replacement for a Setra design that faced declining sales over time.