I'm not sure what you're referring to, the agricultural sector in Europe is rather strong. The US is the world's top exporter of food, but the Netherlands come second.
Europe's agriculture sector is strong largely because of tariff and political protections that keep out competition. The EU's agriculture tariffs are about 100% higher than the US.
The US and Australia have the lowest agriculture tariffs of any major economies or groups such as the EU. Drastically lower in fact. Russia for example - a wheat juggernaut now - has agriculture tariffs over 3x that of the US.
Having your own food supply is far more important then having a free agricultural market.
Also, it's not like the US is not guilty of this either, just look at it's massive corn subsidies.
