321,216,397 according to the US Census clock. I will repeat the analysis I showed above:
Wikipedia lists that there are 327,577,529 cellular phones in use in the United States. 44.2% of those should be Apple iPhones according to the statistics reported by the carriers. However, a lot of those cellular phones in use are still dumb flip phones or plain candy bar phones. . . that's estimated to be somewhere around 65,000,000, so let's subtract those dumb phones from the 327,577,529 - 65,000,000 = 262,577,529. 44.2% of that number of smarter phones is ~116,000,000. Ergo, 100 million Apple iPhones is not out of the question, in fact, it is a low estimate. Heck, Apple sold 48.6 MILLION iPhones in just the last quarter alone!
Why so many more cellular phones than the population? Because they are counting cellular connections and many people have more than one, such as my girlfriend who has two, one supplied by her employer for work and one personal. Also every tablet that has a cellular connection is counted as a cellular phone. Laptops often have cellular connections. Every wireless alarm system is a cellular phone connection. . . and many traffic signals are on the cellular system.
Thanks.