If war occurs I would think it's important to note who starts it; who attacks who - not just assess the regional capabilities. I say this since the US is a NATO member (and its key contribute), and if attacked it can invoke Article 5 of the NATO charter to summon allies into the conflict too (it can invoke Article 4 if it feels threatened to ask for support too).
This force would include Turkey, who could provide the US with warships and access to airbases, nuclear armed France and the UK, who would also supply logistical support, ships and subs - air assets too based out of regional nations and some other minor nations such as Norway and Italy, who could also provide logistical assets, air assets and intelligence.
NATO partners such as Sweden and Australia would be called upon too.
I feel this dynamic is often overlooked, and the US has been historically reactionary, so it's unlikely to fire first. WWI, WWII, Korea, Iraq wars, Afghanistan, they were in response to another nations aggression. Vietnam is an outliers.
This historical reluctance to make the first move increases the likelihood of NATO involvement.
@Nihonjin1051 - thoughts on this dynamic?