Decades ago engineering salaries were a fraction of what they are today, developing countries did not have computing and educational infrastructure, and we had worse solutions to the logistics challenges from off-shoring.
It is increasingly difficult to justify the US salaries and I'm not sure that the talent pipeline in the US is so superior to make up for it.
As folks optimize for getting these high paying jobs it is increasingly difficult to find someone who has legitimate problem solving skills vs someone who has invested a lot of effort into looking hireable.