I propose that we set aside a large swath of land for them to colonize from scratch and prove to the world how good their system is. By their account, their new nation will be surpassing ours in no time. We'll all promise to join once they prove it works.
If the United States had been forced to "start from scratch" to prove how much better democracy was than monarchy, where do you think the U.S. would be today?
A neat thing about an-cap is that the "cap" side is already pretty well developed, and as I mentioned earlier, it may very well be possible to gradually remove mechanisms of government coercion without first dismantling our society or starting over at all. Acknowledgement that government coercion is immoral, and a willingness to limit the powers of government accordingly, is all that is really needed.