With regard to being a citizen of the world, as opposed to being a citizen of America first and foremost, that certainly is a contentious topic! Back in Vietnam (I was in SAC/TAC and therefore way up there above most of the REAL fighting) I was an avowed young anti-war proponent, and as an idealistic YOUNG American (from Berzerkeley) I was decidedly left of center in my political outlook. I also fancied myself also a 'citizen of the world', following ancient Greece's Diogenes the Cynic (4th Century BC) who famously posited "I am a citizen of the world ('kosmopolites')" and I still do within a certain context. Ironically, I came from a family with a long tradition of military service (paternally Irish American) and my father himself was a veteran of the Spanish-American War (1898).
However...big pause for a deep breath...in the subsequent 57 years since that time, my political orientation has changed remarkably (as might reasonably be expected, given the acquisition of greater understanding, maturity and experience in the world that usually correlates with advanced age). Today, as a moderate conservative, although I still acknowledge the importance of maintaining a globalised regard for the overall 'family of man', and despite a loathing of the narrow-minded Philistinism of America's corporate materialist/consumerism, I retain a profound regard for what many refer to as 'the Great American (Political) Experiment' and certainly hope that America may still redeem itself, despite all the often well-intended but radically misguided disregard for racial and social ecumenism that is so faddishly popular now.
Toward that end, you might be interested in Victor Davis Hanson's excellent (2021) book, 'The Dying Citizen'. I certainly found it more than illuminating, myself. In two words (remarkable for me!), "Pithy, illuminating!"
I am reminded always of Christopher Hitchen's words, from his 2008 WSJ commentary (https://www.wsj.com/articles/SB120062413171299477 ), "People who think with their epidermis or genitalia or their clan are the problem to begin with. One does not banish this specter by invoking it."
Be well and aloha nui loa in 2022, -K2