The problem is that politics are so corrupt/inefficient in the US that the projects go 4x over budget/time with no consequences for the politicians/bureaucrats/contractors who let things like this happen.
Just look at the Honolulu Rapid Transit Projects and California High Speed Rail projects.
The overruns in California (relative to European norms) have been attributed to: Higher property prices, mountain ranges, and legal challenges (from property owners, environmental groups, and so on).
If you have specific information on "corruption" then you can update the Wikipedia article on the project here:
Even ignoring the "expected" inflation of costs. IMO the bottom line with California HSR is it would require far more tunneling than is feasible to construct. They studied it extensively, and LA-SF high speed rail just didn't make sense.
Just look at the Honolulu Rapid Transit Projects and California High Speed Rail projects.