With the US out of NATO, USA aggression towards a NATO ally would provoke a response. Also, NATO is not involved with Ukraine. This means that all of NATO can focus on USA aggression. Considering the significant force difference between a non-NATO USA and the rest of NATO, I imagine that nuclear response as an opener is heavily weighed. Glass Washington D.C., then ask if the USA would like to retreat to US lines before they glass NYC. Primary response would be through UK nuclear submarine along the Atlantic.
With the US out of NATO, USA aggression towards a NATO ally would provoke a response. Also, NATO is not involved with Ukraine. This means that all of NATO can focus on USA aggression. Considering the significant force difference between a non-NATO USA and the rest of NATO, I imagine that nuclear response as an opener is heavily weighed. Glass Washington D.C., then ask if the USA would like to retreat to US lines before they glass NYC. Primary response would be through UK nuclear submarine along the Atlantic.