Android is now the most popular smartphone operating system in the US, on the basis of the number of folk using it, at least. According to market research company Nielsen, 37 per cent of US smartphone owners have an Android-based handset, as of March this year. Apple's iOS is second, with 27 per cent of the US smartphone …
Patent lawsuits will sort this out.
The U.S. market does not necessarily reflect the world market
The U.S., even the North American market, do not necessarily reflect world trends since the carriers position in the mix is more of a determinant than in the European or Asian markets.
Therefore it can be inferred that Neilsen, or whomever's, numbers are distorted to a degree.
The Apple OS market is monolithic whereas the Android market offers users a wide range of choices allowing them to select hardware most suited to their needs.
Whilst RIM might be facing challenges in it's home continental market it sure seems to be doing well in other parts of the world.