I found a USDA publication [1] which is a little dated but raises a large number of factors that affect food household expenditure differences between the US and EU. Broadly speaking these are:
- Food prices inc. agricultural protection & consumption taxation;
- Income;
- Food availability;
- Consumption patterns;
- Preference trends inc. health, food safety, production process & taste;
- Demographic trends;
- Retailing & regulation (e.g. consolidation laws).
Some of the factors it highlights that may cause lower expenditure on food in the US than in the EU are:
- Lower food pricing due to protection & taxation;
- Food safety concerns in the EU since mad cow disease and dioxin in chicken feed (and foot & mouth disease in the UK) leading to lower confidence in food supply regulation;
- Greater willingness in the EU to pay more for higher animal welfare in the food chain;
- Higher proportion of organically grown food across the EU and differing definitions of "organic";
- Longer history of consolidation laws in the US.