Is "America First" UnChristian?

Peter Leithart has a piece in First Things, On Trump & Trumpism, that's probably a pretty good summary of what many practicing Christians, or at least practicing Catholics, think about Trump. It's an open-minded and fair-ish read of the President's virtues and vices, and why Leithart is wary of him, but maybe cautiously optimistic about his presidency.

There are things he says I both concur with, dissent and partially dissent from, but I want to object strenuously to this assertion:
even in the best of circumstances “America First” is not a Christian slogan or outlook. Whoever occupies the White House, it's “kingdom first.”
I'd guess that many if not most pious Catholics I know would agree wholeheartedly with those two sentences, and I think therein lies the reason pious Catholics are often abjectly stupid in politics, a field where they are called to be wise as serpents in addition to harmless as doves. I think it's also a principal reason why our American bishops, even though I admire many of them for their courage and orthodoxy and personal virtue, on the whole have a deleterious effect on American politics.

Properly understood, "America First" is the only attitude a President qua president can have. If you are not capable of defending the good of American citizens and America as a whole first and foremost, you ought not to run for office, as that is the precise job description.

Properly understood: "America First" does not mean my country right or wrong; it does not mean my country in contradiction of the moral and natural law; it does not mean my country without due respect for the just claims of other nations and individuals. It does not mean jingoist inability to appreciate the gifts and goods of other nations or cultures, or inability to learn from them. Observing the demands of justice, morality, the common good and constitutional order are in America's (or any nation's) long-term best interest.

Of course, qua human individual with a soul that will spend eternity in heaven or hell, any given President would be foolish and wicked to lose his soul for Wales. So yes, qua individual, he must govern "for the kingdom" -- meaning, he must follow the dictates of an upright conscience when the thorny decisions arise.

However, the instant a President (or his followers) thinks his political acts are "for the Kingdom," he has moved beyond the political order and is asking politics to do what it by nature cannot do. Politics by itself cannot make men moral, nor can it immanentize the eschaton. It can only provide the tranquility of order and the conditions of liberty that leave us free to use our freedom for moral ends. We must observe a space of "legitimate secularity" as BXVI used to remind us.

Such a president would also be guilty of colossal hubris. As Lincoln said when someone prayed that God would be on our side, "Let us pray rather that we are on God's side."

Nor can any President try to govern with the generic interests of the entire world in mind. We would rightly criticize a father who fed the neighborhood at large before feeding his own children (the moreso in time of famine). Not because his own children have more value in the eyes of God than anyone else's, but because his precise job is to love and look out for his own children -- the presumption being that if he takes care of his family, they will not be burdensome to the rest of the community and the community can concentrate its charity and its emergency measures on the truly needy (to cite the reason most relevant to the common good, and leaving aside a discussion of concentric circles of relationship and duty and what parents owe their children).

I'm afraid far too many Christians mistake the small-c catholic "neither gentile nor Jew" demands of charity with the corrupt and cynical cosmopolitanism of progressivism and the huge, trans-national corporate behemoths that have no allegiance to anyone, only to their bottom lines. But you can't be a good citizen of your own country if you fancy yourself a citizen of the world. The fact that a Christian knows this world is not his ultimate home doesn't relieve him of the duty to be fully engaged as a citizen any more than the fact that his children are destined for eternity entitles him to be cavalier about their physical well-being.

Without saying more about it, in this regard I like to think about how Polish St. John Paul II was, and whether that strengthened or limited his ability to love universally. And similarly I think of the example of Benedict XVI, who could not have been more German, or more specifically, Bavarian.  It does not detract from the wholesome diversity of the world for Americans to be fully and whole-heartedly American. On the contrary, it helps others rise and find their own wholesome identities.

I think this is what President Trump had in mind in his excellent speech in Warsaw in the moving passage about Polish heroism that was really a call to every decent person in the world to quit apologizing for existing, and learn to be who you are:
Together, with Pope John Paul II, the Poles reasserted their identity as a nation devoted to God.  And with that powerful declaration of who you are, you came to understand what to do and how to live. 
Democracy requires a demos, as Sir Roger Scruton has said. And the role of the American president is to serve and protect the American demos*.

*For the benefit of Peter Beinart and the similarly obtuse, this includes American citizens of any color and creed, natural born or naturalized.