I'm skeptical about taking this statistic at face value. For most Europeans, wouldn't healthcare and some housing costs be subtracted from their median disposable wage as a part of taxes? And that wouldn't be true for Americans, right? Unless I'm wrong and something like subsidized healthcare is added to disposable income as a transfer, wouldn't this measurement provide a falsely inflated disposable income for a country with less social spending like the United States?

This is all coming from an American, so I'd love to be proven wrong, but it seems like Euros are generally far more satisfied with their standard of living than Americans are. I don't have a study on hand for that though - maybe I spend too much time on Twitter.