rango - 11:32 am on Sep 14, 2012 (gmt 0)
I don't think there's enough evidence that the bounce rate is used in this way to justify blocking entire countries. Matt Cutts stated that bounce rate is not used as a factor (at least not as measured by GA).
I think it is worth focussing on engagement as much as you can and bounce rate improvements overall are an indicator that you're doing something right. But just looking at GA bounce rate numbers and then blocking off whole countries as a result seems wrong.