There may be some upside to renounce a citizenship to do with avoiding extradition. But unless you plan to get involved in criminal investigations, it's probably not worth it.
If America would get a draft again, could a dual citizen be drafted?
Yes; as far as the U.S. is concerned, you're a citizen, with the same rights and responsibilities as any other. If there's a draft, you'll be called upon.
If that were to happen, there would definitely be an upside to renunciation. ;-)
Just watch out for when both sides call a draft.
And worse, go to war with each other. It happened back in 1812 you know...
Then you are a double-agent -- for both sides.
Additionally, my brother became a Canadian citizen (born U.S.), and again had no problems; Canada didn't care about his U.S. citizenship, and the U.S. doesn't care about his Canadian citizenship. He could officially renounce his U.S. citizenship by walking into a consulate and doing so, but there's no up-side to it.