It's hard to imagine that this will actually come to pass but it's certainly an interesting diversion. The 1,776 foot tall building proposed as the world's tallest building still would be as tall than North Dakota's 2,063 Foot KVLY TV Tower.
The Warszawa Radio Mast in Plock, Poland, standing 2117.3 feet was once the highest but collapsed in the 1990s.
In the for what it's worth department Knoxville's WBIR TV has a 1,750 foot tower on House Mountain (combined with its Smokies foothills base pushed it to above 3,000 feet above sea level).
For search purpose here's a brief clip on the WTC proposal:
The move came yesterday when officials overseeing the rebuilding of Lower Manhattan agreed to hire Studio Daniel Libeskind, the Berlin-based firm whose plan for the site centers on the excavated pit at the trade center, ringed by glass towers that swirl upward to a 1,776-foot spire.
The Libeskind design was considered the front-runner for weeks, although a rival plan by an architecture team called Think, which featured two soaring latticework towers called the World Cultural Center, collected strong support as the decision neared. Ultimately, however, rebuilding officials voted in favor of Mr. Libeskind's somber treatment of the memorial and the incorporation of an active street life in the commercial portions of the site.