Why Arizona?
EnviroMission have being promising to build a 1,000m tower "next year" for this project, in Victoria (Australia), just south of the Murray River, for the past eight or more years, but they never got started. Construction costs currently are probably a fair bit cheaper in the US than AUS, but this has not always been the case.
There was never any explanation for the continuous postponements. I have seen the publicity pictures before ...