The future of a nation which excludes God is dispersion (Gn 11:9), not unity. If a nation's faith in God is not firm, that nation shall not be firm (Is 7:9). "A nation of firm purpose [God keeps] in peace; in peace, for its trust in" the Lord (Is 26:3).
Any lasting unity comes from the Holy Spirit, Who is the Source of unity (Eph 4:3). A nation seeking this lasting national unity must focus on lifting up the name of God, rather than making its own name great (cf Gn 11:4).
The most patriotic thing we can do for our country is to make Jesus the Ruler of our life. "He is the blessed and only Ruler" (1 Tm 6:15). He is the Way to national security (Jn 14:6). The next most patriotic action we can take is to lead many others to Jesus. Jesus brought together such diverse people as radical patriots (Simon the Zealot) and people who sold out their patriotism for profit (Matthew the tax collector). Jesus overcame the incredible chasm between these two men and molded them together to become part of the foundation of the Church (Rv 21:14).
In the USA, we proclaim in our pledge of allegiance that we are "one nation, under God." In the Sacrament of Confirmation, we pledge to be soldiers of God, under His rule. Let's live our pledges and live under God's rule. Make Him Lord of every aspect of your life (1 Pt 1:15). He will use your obedient life to build "a holy nation" (1 Pt 2:9).