What are the differences in the two as far as spirituality?
Plus, are melkites about the closest to the Greek Orthodox as a catholic can get in the USA?

John,

I'm a bit uncertain (heck, completely uncertain) as to precisely what you mean by the question? Define your terms a bit, please.

Are you using 'Greek Orthodox' to mean the GOAA or generically, as was once common and now rarely used, to mean all Eastern Orthodox faithful?

I suspect the former, but nothing asked here can always be presumed to be meant simply - a truism most of us learned a long time ago.

And, by 'closest' do you mean liturgically (as far as praxis), spiritually, theologically, what?

In this case, I presume the first of those, but the same caveat applies.

If my presumptions are correct and you are asking whether Melkite liturgical praxis is closest to that of the Greek Orthodox, I'd say 'probably'. Except for the single parish of the Italo-Grieco-Albanians, the Melkites are the only non-Slavic Eastern Catholics in the US, the only ones who liturgically serve according to a Greek usage (the Grieco-Arabic rescension of the Byzantine Rite).

But, I'm unsure what that means or proves. A Greek Orthodox in the US who translated to the Catholic Communion would probably find themselves ascribed to the Melkite Eparchy, for lack of a Greek Catholic presence in the US, and would probably feel most at home there versus another of the EC Churches - lots of 'probably'.

Many years,

Neil