I would caution that "economic mobility" is a term of art that does not mean what most people intuit it to mean, usually conflating it with the ease of improving absolute financial position. You can easily improve your absolute financial position and still have "low mobility", and you can have "high mobility" while having minimal opportunity to improve your financial position. A limitation of economic mobility is that it is only comparable between countries with similar geographic/population size and with similar levels of wage compression. The US is an outlier in all three terms.

Average people want the opportunity to significantly improve their financial position, and economic mobility doesn't measure that. As a country, the US outperforms most other industrialized countries at the former.