I want to be careful when I say that the United States is not, has never been, and never will be a Christian nation. My intent is not to express a desire that it actually become a Christian nation, for that would be to express a desire that can never become reality. In the first place, whatever authorities it would be constructing such a nation would be the ones defining "Christian," and we all know the ugly directions that endeavor can go. We certainly don't want a theocracy until the Lord himself institutes that new heaven and new Earth. Otherwise, the Lord looks way too much like the people (usually men) making the laws. Secondly, no human governmental authority could ever be perfectly "Christian." Christ is Lord, and no Caesar ever can be.
That said, there are basic precepts in scripture that express God's desire for compassion, equity, and justice, and I do desire that our laws and institutions reflect those sentiments. And when it comes to migrants and LGBTQ+ folk and women and children and the poor and (insert minority or marginalized group of your choice), our laws rarely reflect said compassion, equity, and justice. In this sense, our justice system certainly does not reflect the heart of God.
One recent news story that highlights how far our justice system strays from the heart of God for the marginalized and oppressed is that of the geology professor who was arrested for giving water to migrants in the Arizona desert, and who now may be facing 20 years in prison for such basic compassion. You can read about (or listen to) that story below:
Compare our nation's laws outlawing basic human compassion to migrants to the Lord's heart:
“Give justice to the weak and the fatherless; maintain the right of the afflicted and the destitute.” - Psalm 82:3
“Learn to do good; seek justice, correct oppression; bring justice to the fatherless, and please the widow’s cause.” - Isaiah 1:17
“He has told you, O man, what is good; and what does the Lord require of you but to do justice, and to love kindness, and to walk humbly with your God?” - Micah 6:8
We may not be able to, or want to, create a Christian nation, but we can certainly make laws that do not punish people for simple acts of compassion and kindness, especially to the "least of these." After all, it was our Savior himself who said (when separating the "sheep" from the "goats"), "For I was hungry and you gave me something to eat, I was thirsty and you gave me something to drink, I was a stranger and you invited me in, I needed clothes and you clothed me...."