Generally speaking, it is not possible to identify Christian Nationalists visually. With a few exceptions (e.g. some of the more radical ones carry guns and wear military fatigues, etc.), they are like other Americans. You could be neighbor to one and not know it. It is primarily their speech, news preferences (Fox News), religious habits and voting habits that distinguish them from others.
Regarding speech, here are a few talking points about which they might be especially vocal and/or sensitive:
America is a ‘Christian nation’ and the government should keep it that way.
Crime is rising because Democrats have been “soft” on crime
Inflation is due to excessive government spending, and wage increases
Liberals voted to hire an army of IRS agents who will audit and harass the middle class
Public health rules, criminal justice reforms and the purported excesses of woke culture
Opposed to diversity, equity and inclusion policies
Liberals are leading America in the wrong direction
Millions and millions of illegal aliens pouring across our border
Opposed to race and gender indoctrination.
Corruption and extremism of radical Democrat party
Smaller federal government
Traditional family values
Personal responsibility
Strong military (peace through strength)
Limited access to abortion
Law and order
Freedom of religious speech
Deep state government
Demonic left-wing liberals
Conspiracy theories
Lower taxes
Free market economy
Anti-vaccination
States rights
Parental rights
Religious education and homeschooling are good, public education is bad
Academic liberalism
Climate change is a hoax
Marriage – One Man and One Woman
Liberally biased news media
Private Property Rights
Limited sex education in schools.
Second Amendment and Gun Rights
Anti union
Limits on welfare programs
Stolen elections
Government Spending out Of Control
Opposition to LGBTQ+ rights
Religious freedom
January 6,2021 was a peaceful demonstration — not an insurrection.
Government overreach
Mask mandates
Threats from immigrants
Election fraud
While these are common talking points for many Christian Nationalists, it is important to understand that they are not a monolithic group. People who do not identify with Christian Nationalism might also talk about some, or none, of these talking points. But, even if they do not volunteer their opinions about any of these points, chances are that they might agree with most of them if pressed to talk about their political beliefs.
If these talking points do come up in conversations, however, it is best not to engage in discussions/arguments on these topics. Questioning their logic and facts behind their statements will probably aggravate them and trigger them into defending their beliefs with party-line rhetoric. That is not a good strategy for changing hearts and minds. Better to listen thoughtfully. Give them the same kind of respect you would give to someone who embraces a religion different from yours or a child who is involved in a cult.