Don't know if Interwetten is available in North America; it would be my choice as a European. [1] Also, William Hill has a politics market.

PredictIt is a US-based prediction market, which should work in Noth America, but is not available for many jurisdictions in Europe. [2]

[1] https://www.interwetten.com/ [2] https://en.wikipedia.org/wiki/PredictIt