> After 16 months in July 2019, a report was produced but it did not provide the comparisons requested by Congress. Rather, the GAO in its report said making the comparisons was too difficult to obtain meaningful results [...]

As an outsider from Europe, let me try.

1. It always seemed to me that the litigious nature of doing business in the US must be costly to society. The thinking of "If anything ever happens to you, someone owes you money". Lawyers are needed in anything of consequence, and it leads to lots of overhead, distraction and unnecessary work to avoid the possibility of being liable for anything.

2. Then there is corruption. The US ranks lower than most european countries on corruption (https://en.wikipedia.org/wiki/Corruption_Perceptions_Index). The article hints at that, mentioning "politicizing" of infrastructure projects. That also costs money to society.

3. Then there is lack of competition. Because antitrust laws have not been enforced for decades in the US (not anywhere else too btw), I suspect that big infrastructure projects are getting distributed among a few large companies, who don't actually compete; they'll all make good money and pay their C-level execs well.

There may be other factors like healthcare costs, and unions adding to costs, etc, but those seem to be a result of the above, rather than a root cause.