"He will use his powers, he says, to build a country where "you can make it if you try.""
First of all, what makes him assume that this country isn't already a place where you can make it if you try? Everything I've seen strongly indicates that it is. That is, after all, the central characteristic which has drawn immigrants here for centuries - legal and otherwise. They've come here for opportunity - and it's more readily available here than any place else I've ever seen or even heard of.
Second, granted for the sake of argument (and only for that purpose) that America needs to be built into this rather mistily-alluded-to Utopia, what makes Obama assume that his powers will be any use in bringing it about? The office of the executive doesn't have anything approaching that sort of power. Nor do his compatriots in the legislature. To be honest, those would be the powers of a god, not of a legislator or executive.