Unkind lessons from history:
When your country is the global hegemon it's easy to be magnanimous, because nobody can see the future where you'll some day be #2. It's also easy, being #1, to give away the fort. The Machiavellian thing to do would be to take advantage of the presumably temporary nature of the hegemony and wipe the field clear of your competitors, which is admittedly very difficult to do.
The Paul Kennedy (Rise and Fall of Great Powers) conclusion is the US needs to balance internal affairs and external commitments and military spending as best as it can, otherwise the decline will be hastened.