Earlier quoted context omitted.
In the U.S.A., people use iMessage by default, because they use text messaging. People don't use texts in Europe (we use WhatsApp and similar, but WhatsApp by a long margin). The reason people still use texts in the U.S.A. is up for debate, and it's something I've thought about for a long time.
US was a first-mover and had early telcom penetration, so SMS became culturally ubiquitous since it was the tech of the era. Late-movers could skip that and go straight to data-based telcoms and never had to deal with the critical culture mass of SMS while the US was stuck bolting on to and bridging SMS. It's like being able to skip over copper and go straight to fiber optics.
Telco penetration – yes, the US had a upper hand. SMS (and messaging) – no, the US lagged behind for many years.
DAMPS (the 2nd generation mobile standard in the US) and early CDMA US networks did not support SMS/text messaging at all whereas European telco users had already been happily texting each other since the introduction of GSM (2G, early 90s). Americans used the phone answering machines and the voicemail instead, which has been widely depicted in Hollywood movies and was a source of amusement for non-US watchers.
GSM was later introduced in the US with very limited coverage on east and west coasts to support roaming for European users (roaming was non-existand in DAMPS and in CDMA networks, either) and operated on a frequency band (1900 MHz) that was incompatible with GSM 2G 900/1800 MHz bands and required a tri-band handset but it introduced SMS to the US mobile networks users for the first time.
There was also a pricing barrier that hampered adoption of SMS in the US – European and Asian users had to pay for SMS's they have sent, but not receive one (the cost was zero), whereas the US users had to pay to send AND to receive text messages. Gradually, 3G came to the US, brought SMS out of the box, gradually replaced DAMPS and CDMA networks in the US and the US users got SMS out of the box.
The US did not lead the cultural revolution that SMS had brought about in Europe/Asia.