Neilson: In the US, Samsung sells more WP than HTC; 58% of Nokia
I took the image of said chart into paint and did a pixel by pixel measurement that resulted in the following.
Windows Phone US % of total market share
HTC's: 0.44% (18.8% of WP US)
Samsung: 0.70% (29.9%)
Nokia: 1.2% (51.2%)
Given how little Samsung seems to give a care about WP (given their Android marketshare, it's obvious why), it's surprising to see their presence. This also puts Windows Phone's penetration in the US (as of Q2 2013) at under 2.5%. This seems like a retraction from the 3% they had this time last year. The one positive is that Nokia's market share is growing, but given how little everyone else invested in WP... this isn't surprising.