https://en.wikipedia.org/wiki/List_of_megaprojects#North_Ame... suggests: CityCenter in Las Vegas, Brickell Key in Miami, and Battery Park City in NYC as recently completed megaprojects in the US. (The last has been in development for a long time.)

It also lists the Hudson Yards Redevelopment Project as an on-going $20 billion megaproject, which broke ground in December 2012 and appears to be doing well. It's the largest real estate development in U.S. history.