iMessage and iPhones being 'more secure' is simply not true. I know it's being thrown around a lot, but e.g. Pegasus famously had zero-click exploits for iMessage.
I'm feeling you are assuming that the alternative to iMessages in Europe is SMS. It's not. The alternative is WhatsApp, Telegram, Signal, Facebook Messenger, etc.
Signal, WhatsApp, and iMessage frame privacy from the service operator as the norm, while the others relegate it to some “I’m being sneaky now” switch.
Framing fundamental privacy measures as sneaky mode is actively harmful to their broader adoption, paints a target on the few people who do have dire need for protection, and makes us all vulnerable to efforts to legislate against what progress we’ve made.