The biggest EU defence needs are two: securing oil ingress from the Middle East and securing resource ingress from Africa. Without the US 5th fleet, Iran or any other regional power could shut down oil ingress, pitching the EU into a sizable (-30%) GDP recession. Instability, of which there is plenty in the Middle East, could do the same.
Same for Africa, with the added threat of Chinese competition for the same resources. Without those raw materials (minerals, uranium, some oil and gas) European manufacturing doesn't have a future. Hence the constant French and American interventions to stabilize various African states and their tight relations with their governments.
