quality was the keyword here. Yes people spend less on average, but the quality of what they buy is awful. I lived 20 years in various countries of the EU and 10 in the US. Based on my XP it is more expensive in the US to get the same quality that's it. I don't have data or fancy metrics to back it up, it's just my empirical observation :)
The United States (as a whole) spends less of a % of income on food than any other country