Nietzsche
Banned
I'm no expert on this time-period, but I don't think nations, other than for the European power balance, think this way. This is way too global of thinking, too early. The US or Confederacy isn't going to be looking for an ally to divide the world together with.
You're right, they don't tend to think in those terms. But in the case of Germany and the US, if France intervenes in the Civil War and causes the Rebels to, well, remain a country, they both have an enemy they hate with the power of a million suns going super-nova at once.
Gravity is not the most powerful force in the universe. Mutual hate is.