I definitely welcome further integration of the foreign policy and defense structures of the member states of the EU, i.e. a further consolidation of the Common Foreign and Security Policy. However, I think it would incredible irresponsible and dangerous to abandon NATO, at least until a credible alternative exists at the European level.

A key problem with abandoning NATO is that the aggregate strength of the European members of NATO has been increasingly meager. Part of the problem is the relatively low level of defense spending in Europe, as only three states are currently even fulfilling NATO's guideline of 2% defense spending (UK, Greece and Estonia). Consequently European security continues in part to rely heavily on the US, especially in terms of power projection and global logistics. Moreover, even if the larger European states stepped up to help offset the deficit of the US leaving, a united European defense force would still inevitably be weaker than the entire North Atlantic Alliance. So then this begs the question, why would we ever wish to do away with the most powerful security alliance that can safeguard our international security.

However, the reduction in total power is not even the biggest concern of switching from NATO to a Europe-central defense pact. The biggest problem is that time and time again over the last few decades European states have shown that we are not yet capable of ensuring the security and stability of the continent. The first major test after the fall of the USSR- the Yugoslav Wars- were a complete disaster as far as the European response went. Different member states sent conflicting messages different states supported different belligerents, etc. All in all it was a clusterfuck and it was only the US led diplomatic effort that culminated with the Dayton Accords that ended the conflict. The current response to the crisis in Ukraine is just as pathetic as the extremely low level of resolve or unity at the European level only encouraged Putin to increasingly escalate the crisis.

Now you might argue that neither Yugoslavia nor Ukraine were part of the European security umbrella and the situation would be different if it was an EU member state whose security was at stake. I hope that this is true, but frankly I am not yet convinced that Europe would be capable of a sufficiently robust and coordinated response to protect one of its members. And this is the biggest problem, others will have similar doubts, which is a recipe for disaster when deterrence is rooted in the credibility of action of a defensive alliance. No, while I wish to see Europe continuously integrate its defense forces and to coordinate its foreign policy more closely, I certainly don't think it would make sense to dispense with the credibility of NATO's force in favor of a much more vulnerable European defensive pact.