Many wrongly assume that God's presence has to do with judgment rather than blessing. Is God's presence good or bad? Both … It's frightening in regard to judgment, "The idols of Egypt will totter at His presence" (Isaiah 91:1), but it's very good in relation to His presence in the life of a believer.
America is, of course, not the only nation blessed by God. Our people are not the only people loved by God (cf. John 3:16). But to the degree that we are endowed with natural resources, productive and resilient people, and blessings of liberty, I believe it behooves us to ask why.