Immigrants being nationalized swear an oath of allegiance, not to the flag, not to the military, not to the national leader, not to a cultural group or historical victory or nationalist value set or symbol or even to a vague “United States.” They swear an oath to the US Constitution.
I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state, or sovereignty, of whom or which I have heretofore been a subject or citizen; that I will support and defend the Constitution and laws of the United States of America against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I will bear arms on behalf of the United States when required by the law; that I will perform noncombatant service in the Armed Forces of the United States when required by the law; that I will perform work of national importance under civilian direction when required by the law; and that I take this obligation freely, without any mental reservation or purpose of evasion; so help me God.
That seems an expression of patriotism we don’t see much of among the native-born population.
Pledging Allegiance to the U.S. Constitution – The Atlantic
How patriotism among American immigrants is uniquely linked to the country’s founding document
Maybe not the general population, but as a member if the military, that's the oath I swore.
+Harold Chester Most governmental oaths (extending that to the military) swear something similar. I'm not one for gratuitous oathmaking, or repeated ritual of such a fashion, but I find it more refreshing and valuable than pledges to a flag (let alone public displays of allegiance during a national anthem at a freaking sporting event).