> Simply put, there's no first-world country in the world where top talent can earn even close to a US salary, which largely due to the fact that US is relatively permissive towards large income disparities.

Why do you think it's A -> B and not B -> A? What factors of the US being permissive towards large income disparities do other nations lack that prevent them from paying equivalent salaries.

One specific thing I've heard which makes sense to me toward explaining the salary gap is the US tends to have at-will employment while other nations make it more difficult to fire people. I wouldn't personally classify as promoting income disparity though.