Your citation points out that a McMeal in Denmark costs around 12$ while in the US costs around 10$.
Even if you blindly assume that revenue is tied to salaries, are salaries in the US only 20% apart?
Your citation also points out that a McMeal in Spain is cheaper, and I'm sure that quality of life + benefits in the US is even in the same division, specially give that Spain has free healthcare for all.
The truth of the matter is that workers in the US are massively exploited and abused, and that as a deep impact on everyone's quality of life, even the privileged.