To ensure that Europe will protect the US?[0] Seriously, though, you realise that NATO and the EU have different members, right? If Russia invaded Finland, th

To ensure that Europe will protect the US?[0] Seriously, though, you realise that NATO and the EU have different members, right? If Russia invaded Finland, then Finland (as a non-NATO EU member) would not be able to invoke Article 5 to call on the defence of all NATO countries, but it would in theory be supported by an EU military mission. I guess you're asking "Why aren't all EU members also NATO members?" to which I don't know the answer, but I think an answer would start with "It's complicated..." or "Historically...". [0] https://www.nato.int/docu/update/2001/1001/e1002a.htm https://www.nato.int/docu/update/2001/1001/e1002a.htm