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.

Apologies I missed copying the actual reference in my last post: https://www.ers.usda.gov/webdocs/publications/40408/30646_wr...