The US, meanwhile, has been engaged in wars almost non-stop since WW2. It's "unprecedented world peace" for for only a select few nations.
And, most importantly, the costs of failure have gone up dramatically with the invention of nuclear weapons. The Cuban Missile Crises is just one of several near-catastrophic events. Sooner or later, we will get a madman in a position of power, fall victim to a misunderstanding, or suffer a technical failure.
And that'll be that...
You don't need territory (at least at a price that steep) and you certainly don't need slave labor in 2018.