I too have read explanations for the USMC deployment to Helmand, politely but firmly pushing the UK & partners aside.

Yes, unity of command - even within the US military - appears to be lacking. What our enemies made of this and the ANSF is a moot point.

What I do not understand is why first the UK, then the USA decided Helmand Province was more important than Kandahar Province. Helmand has only 3% of the Afghan population. Yes the Canadians had a small battle group there and much later, I suspect in the surge, a Stryker Brigade went there.