Hi @Dr_Fred. You're right, the UCI WorldTour calendar (http://www.uci.ch/road/) is mostly a European affair. There are two Canadian races in September. The classics are there and so is the bulk of the interest.
There are several big U.S. races including the Amgen Tour of California (http://www.amgentourofcalifornia.com/) this month, May 15-22, that will have many top UCI WorldTour teams, but no official UCI WorldTour designation - for the men, that is, as the AToC's women's race is a Women's WorldTour 2.WWT Class!
You should also see the US Pro Road Tour scheduled (http://usacycling.org/prt/). Typically not UCI WorldTour teams, but UCI ranked pro racing in events like Redlands Bicycle Classic, Joe Martin Stage Race Tour of the Gila, Winston-Salem Classic Road Race, Philadelphia International Cycling Classic, and Cascade Cycling Classic.