As for direct liability costs, I can't remember if I've read any recent studies of those. But I went to law school (I'm not an attorney, though) and several of my family members are tort lawyers, and I can tell you from everything I know and have learned that liability costs are overblown. The fact of the matter is that every society will force negligent businesses to internalize the costs of their negligence. Some countries (esp. common law countries) emphasize the ability of individuals to seek compensation for actual damages. Other countries emphasize prevention and enforce a much stricter regulatory regime. Either way the costs can be considerable, but in any event the U.S. doesn't stand out among developed countries AFAIK.
I just watched the Wizard of Oz this past weekend and in one of the opening scenes Miss Gulch, who was bitten by Toto, threatens to sue Dorothy's Aunt & Uncle for everything they have, taking away their farm. Point being, Americans have always had a somewhat irrational fear of litigation. It's a cultural thing. That same fear existed back in a time when building big infrastructure projects was cheap.
That's luck of the draw, not anyone's aversion to having engineers on a jury.
How do you know that? It seems like a really difficult number to account for like the cost of medical lawsuits. Sure, you can look at malpractice insurance, legal fees, and damages awarded to plaintiffs - but how do you properly count the extra tests, procedures, pharmaceuticals, man-hours, etc. that result from the increased defensive posture of doctors and hospitals?
What you describe could also be understood as an inefficient way of organization that is peculiar to the United States, and a by-product of American business and economic logic. Firms (i.e. vertical integration) exist to reduce the comparative inefficiencies of having separate, independent entities. Most other countries still have huge conglomerates (e.g. Japan, Korea), or contractors enjoy closer and longer-term business relationships.
With rare exception (Berkshire Hathaway, Elon Musk, etc) Americans have systematically shifted toward looser organization of smaller, independent business entities. One of the downsides is the exploding cost of orchestrating these entities for big projects, and the loss of knowledge about how to manage such projects.