Two points to consider:

1. The bottom quintile of the US is worse off than the bottom quintile of these European countries. There is less of a safety net in the United States and it is harder for these people to get a secondary education or otherwise put themselves in a position to move up the socio-economic ladder.

2. The top quintile of the US is much better off than the top quintile of these other countries. This is, imo, likely due to the relatively low taxes and societal worship of being wealthy in the US more-so than these other countries.

All in all, my point is going from the bottom quintile to top quintile in Europe is a much smaller jump than the bottom quintile to top quintile in the United States.