If you’re having trouble interpreting the chart of the U.S. smartphone market released Thursday by Nielsen, think of it as a brownie pan, a spokesman helpfully suggests, not a pie.

And depending how you slice the brownies, Apple (AAPL) is either No. 2 or No. 1 in the U.S.

When all the Android phones are combined, Google’s (GOOG) smartphone operating system is the clear leader. But because so many manufacturers are competing for a share of the Android brownie, and only Apple can make an iPhone, Apple is America’s leading smartphone manufacturer. By a chewy mouthful.

The details (based on a survey of 20,202 Americans in Q2 2011):

• Android has 39% of the U.S. market
• The iPhone has 28% (iPads and iPod touches not included)
• Research in Motion’s (RIMM) BlackBerry is down to 20%
• HTC is tied with RIM at 20%, divided between Android (14%) and various Microsoft (MSFT) Windows smartphones (6%)
• Motorola (MOT) is down to 11%
• Samsung has 10%, divided between Android (8%) and Windows (2%)
• Nokia (NOK) and Palm (HPQ) are those thin slices on the right with 2% apiece