Does Empire Pay?

TPM is holding a forum on Andrew Bacevich's book, The Limits Of Power. Here Bacevich responds to Tony Smith:

What I try to argue is that empire (or at least an expansionist foreign policy) once paid. Indeed, if we cite the Louisiana Purchase as the beginning of serious American expansionism, then it paid quite nicely for at least the next century-and-a-half ... The problem is that for roughly the past four or five decades empire (or expansionism) has ceased to pay. Unfortunately, our political elites, deeply invested in obsolete and bloated conceptions of "global leadership," won't face the facts.