On top of what wmf said, with whatever government investment has or has not already been made, the U.S. has the fourth highest* IPv6 adoption by percentage of requests as of Dec 2013 [1]. That is double what it was just six months prior [id].

Moreover, I doubt the US has as pressing a need to stave of address space exhaustion as do developing countries like China with rapidly expanding internet uptake.

*biased by Akamai's usage rates from country to country, of course

[1] http://www.networkcomputing.com/networking/ipv6-adoption-her...?