.... Story wise there needs to be an antagonist.
I don't put much weight on that. Story here includes many levels. On the level of geopolitics, who was the antagonist the USA needed to have in 1910 for story purposes? A nation state's internal politics is quite likely to prioritize naming some other nation a rival and the most important one, but this is not absolutely bound to happen. A state might be in such a strong position they do not fear anyone rationally challenging them on any front, and thus turn attention to other matters not bound up with international competitive politics. For instance I'd say that in 1910 the preoccupation in the USA was class struggle--lots of ragtag radical groups cropping up or left over from prior cycles pointing fingers at crooked elites, lots of well off people fearing the uprising of the ragtag mob. Very very few people running around denouncing Germany, or France, or Japan, or even superpower Britain, as the enemy, fear of which must dominate the national narrative. I'd say by far and away if you took a poll, more people would list Britain than any other foreign power as the one to fear and oppose. And yet US policy hardly took a hard line against Britain, unless you consider the slogan of "a Navy second to none" as a threat aimed at Britain--even so, our pursuit of that policy did not cause undue alarm in London nor poison relations generally. Despite more Americans agreeing that Britain is the worst in terms of "who should we worry about?" US policy was more favorable than not to Britain.
So it may be true that as in drama, so in real life, nations collectively have a narrative going in which conflict is the essence of story. (People challenge that Aristotelean idea that story is all about conflict, see Ursula LeGuin's "carrier bag theory of the novel" for instance as a fine deconstruction. But this gets pretty deep into literary, cultural and feminist theory after all). But given there must be CONFLICT, the antagonist need not be another nation-state. Given that few nations enjoy the sort of complacent security the USA of the 1900's did , fear of some foreigner or other is quite likely to be high on the list, especially because it is a very convenient distraction from issues some might argue ought to be more salient, such as the plight of the working class or the imminent danger of the rising tide of democracy subverting civilization to pick two sides of another argument. But there is no guarantee a nation will in fact be determined to pick a top foe and then systematically work to spite them.