I'll give them the benefit of the doubt and assume that they they use "Britain" as a casual term for the UK, in the same way that people refer to the USA as "America". And yes, the word "country" is not properly used.

I was very surprised by the thrust of the article however; I had assumed that the US was much more violent. Especially given the dearth of firearms in the UK. If this is accurate, it is extraordinarily puzzling, at least to me.