Quarts into pint pots
It's probably worth pointing out at this point that in the current history curriculum, Prussia, Italy and the United States do not appear either. The only non-British countries to get a name check are India and China (although there are mentions for 'Europe', the 'Islamic World' and 'West African Kingdoms').
For what it's worth, I studied history up to post-graduate level, and I've never studied the birth of Italy, or American history at all, although I did cover Prussian history for A-level (and ended up writing a Finals paper on it, in the absence of any subject I'd actually covered coming up in the paper). I think it's effectively impossible for there to be a comprehensive syllabus for British and world history which can be covered in six years. I also think that if there is to be any part of history which should be compulsory, that part is British history, for all that Aaronovitch dismisses this as "bastard civics".
A curriculum to 14 can only ever be a bare minimum of what ought to be taught. For those who are interested in history, GCSE, A-Level and undergraduate studies can provide an unimaginable breadth of study - my undergraduate degree ranged from a discussion of warfare in post-Roman Britain to a dissertation on a shot down plane in Zimbabwe's Bush War. A young age curriculum is not about setting a limit on what can be learned - it is about setting a basis for what children ought to know. Gove's proposed currriculum may be too prescriptive and too comprehensive, but I don't think that a focus on British history is a drawback for this stage of learning.