> How does having such a large surplus (...)
You should educate yourself. Europe imports around 40% of the agricultural production it consumes.
The "surplus" is referenced in economical value and reflects luxury exports such as wine, which is hardly what keeps Europe alive in case of all-out war.
The whole point of Europe's common agricultural policy is food security including an event of all-out war.
Your comments sound like advocating against having a first-aid kit just because you sell silk scarves.
Please provide some sources, because I think your 40% is also based on monetary and not nutritional value.