"So why even try stopping us? Because if we're not the one country - or, more precisely, the one culture, civilization, IDEA - most fit to rule the world, who is?"
Mind you, I'm not saying anyone actually spoke those literal words in Tocquevillean America. Only that our US history might have attained some breathtaking heights of self-honesty if they had.
But what is it that could produce and fuel such blithe confidence? Anyhow, here's a speculation:
Imagine everything in heaven and earth being as simple and straightforward as, well, the Declaration of Independence. Imagine there being nothing of real, abiding interest in human affairs to talk about (or even, strictly speaking, to think about); nothing to reflect on, or consider, or wonder at; nothing to discover, or explore, or be surprised by (whether pleasantly or otherwise), or enraptured with. Particularly if you're one big, dynamic, superior, human-tidal-wave of a country poised for serious overland expansion. There are no unexpected twists or turns, no strange curvatures of geography or history, no Burkean particularities to understand and accommodate, to be patient with or sensitive to. Indeed, there is no abiding truth - nothing we do or choose or undertake - that can't just as well be conformed to a straight or perpendicular line. Because, you see, it's all self-evident. Those (surely) are the only truths worth believing in, or acting on. And if all you can do is impose them on some stupidly recalcitrant reality (whether natural or human), all to the good. And if you find they can't be lightly interwoven into the pre-existing fabric, or gently seeded into the pre-cultivated soil, why, so much the better. Just slap 'em down, and steamroll 'em over.
I mean, what's the worst that can happen? The "stuff" beneath your feet, or beneath your plans, will either submit to your overriding, commanding, abstracting Will as if it ne'er had nature of its own. Or else it will change you (the Louisiana Purchase, the War of 1812), and all your plans and agendas (the spoils system, the Mexican-American War, the Ostend Manifesto), beyond your every conceivable intention or expectation.