I've thought about that in the past. Not sure I have the answer yet but let me play Jared Diamond for a while.
This mindset is called projection - a typical behaviour of narcissistic individuals. The person who wants to wrong another person projects that intention onto that other person thus providing justification for wronging them aka "you wanted to stab me in the back, that's why I had to do it first". This is a maladaptive defense mechanism that solves two inherent problems for the narcissist - the need for maintaining good image and the need for resolving the sense of guilt and shame.
Narcissists are fundamentally people who are not taught to distinguish shame and guilt and therefore can't accept criticism and treat it as aggression.
On that - note how American Protestantism has a "shame" notion of sin compared to Catholic "guilt" notion of sin. American sin is about rejection of the sinner. Catholic sin is about rejection of sin. American culture is fundamentally a Protestant culture.
I would argue that the US has a greater rate of narcissism in culture as well as greater number of narcissistic individuals in society compared to other countries for several reasons but I'll name three major ones that form a positive feedback loop:
1. Environmental factors.
In Europe or China societal pressure and limited land and economic opportunities caused the cultures to select for social cohesion and order and heavily against narcissism. When internal tension was too high it caused revolutions or war. In America land was unlimited and societal pressure was easily avoided. This is why America has only one internal (major) armed conflict in its history and no revolutions.
2. Personality of migrants.
First settlers were dissident religious fundamentalists. Fundamentalism correlates highly with narcissism. American political system was founded by religious sects and American model of "freedom of religion" differs from French revolutionary "laicite" in that it is a freedom "to" rather than "from" religion. As America developed more people would come attracted by economic prospects. Risks and distance meant that the people who were forced to flee or had high motivation were most likely. For reasons that I won't get into due to space limits both are highly correlated with narcissism. Finally slavery and racism are both highly correlated with narcissism and American state was founded expressly for the protection of slave owners with the help of New England fundamentalists and business interests.
3. Lack of external competition.
Development of American culture was protected by North America's unique geography and lack of developed native cultures which provided lack of external pressure on cohesion and order. Furthermore the native populations which existed were not only small and underdeveloped but also were often the "barbarians" to the previous cultures which would be destroyed or severely weakened by the pathogens brought to America by first colonists, mostly the Spanish. This meant that the fledgling American culture never had to account for a peer rival and often the only cultures that it encountered would be similar to itself and for the same reason (Spanish colonial culture, expansionist native cultures). There's obviously Canada but they don't count.
In short America is a culture that grew out of a disproportionate share of narcissists thrown into safe and rich environment with numerous advantages. Think of a spoiled kid playing a game with cheats so he always wins. American culture is not like other English colonial cultures - Canada, Australia or New Zealand - and it might be because those cultures were limited externally by the British imperial rule.
This probably lies at the core of American culture being the best representation of a "peach culture" - superficially very friendly but inaccessible and hostile at heart. Americans only to be friendly as not to get into (shooting) fight with each other but not as friendly as to have to sacrifice for or share with others who they don't approve because they have almost never had the need to do so while in old cultures this type of cooperation was a necessity whether you liked someone or not.
And it's not just "the enemy" but "the friend" as well.
Americans disproportionately see themselves as a "chosen nation" and are less likely to believe that they should learn from other cultures to improve their own - just think about the metric system - but naturally their ideas are the ones that need spreading.
I saw a clip of justice Scalia expressing the view that European countries don't have full separation of powers because they don't separate the legislative and executive branches in the same ceremonially superficial fashion as the US does. Scalia is a justice of the US Supreme Court so clearly someone who should have the knowledge but he chooses to treat American system either as revelation or if Americans invented it or both.
That's not a good comparison because Space Race wasn't a zero sum game. Soviets "winning" it would have no material consequence as long as US could match them.
America's imperial business like all of politics is absolutely a zero-sum game. China's win is by definition America's loss. Seething is rational and more than you think.
A state is a territorial monopoly on the use of force. An empire is a security provider for client states. Being a monopolist enables to put a premium on your services. When America is forced to compete with China it has to lower its price and improve its service.
However having been the security provider for these contested regions since 1991 created a generation that was raised in conditions of permanent superiority. Before 1991 American interest would always have to contend with either Soviet or British or some other imperial interest as a potential threat. Since 1991 there was no competition and that set the tone for how the relations would be conducted.
Also China makes it harder by playing the "humble" card which forces Americans to change their attitude or risk losing influence. China is aiming upward so they lose nothing by playing "humble" but America must aim downward which makes it a humiliating experience having to renegotiate the relationship and do so with greater humility. Politicians and media people are some of the most narcissistic individuals in every population. That's not "seething". It's narcissistic rage.
The problem however is again broader. British Empire was at its peak in 1900 was fairly comparable to American Empire in 2000 and yet when it began to collapse the average British citizen acted differently from the average American. The elites were seething. The citizens were not. And yet in America so many Joe Schmoes act like they're the nobility losing their titles and lands.
There is a major difference in how American culture shapes perceptions of Americans compared to others and I think it has to do with how this one particular personality trait is selected for by America as an environment and society.
And so my final argument is that if it was a personality trait then it absolutely would be affected by generational cohort and upbringing conditions.
And lo and behold: Boomers are the absolute worst. Millenials (boomers' children) are the second worst. X-gens and in Zoomers aka "crisis generations" are much better with regards to accepting the change. Zoomers are best because they benefited least from America's position in the world and have known nothing but arrogance, war and crisis in their life. It's not "their" empire. It's somehow still the boomers'.
This chart shows data for 2014 - left is annual cohort, right is life duration.
I think the difference between boomers and zoomers is quite distinct.
Anyway... whether my analysis is on point or not "You're nothing special and have to get over yourselves" is not the type of book that is going to sell millions of copies I'm afraid.
This is what happens when Canadians want to be Americans. They should stick to just being sorry.
