it's ultimately up to the airline provider to decide whether to permit people to use their mobile phones to make calls, send messages, access social media, and stream videos, but the EU has made it legal, so, why is cell phone use still illegal in the FAA and FCC controlled airlines?

Boeing and Airbus have reportedly tested the effects of mobile phone signals on aircraft avionics and they have found no significant impact. They concluded that mobile phones do not operate on the frequencies used by aircraft systems, meaning they do not interfere with critical avionics.

Besides, it's a fact that a plane crash has never been directly attributed to mobile phone use, and no peer-reviewed studies have found a definite link between phone signals and disruption to aircraft systems.

https://www.iflscience.com/airplane-mode-is-no-more-in-eu-so-why-are-phone-calls-still-banned-on-us-flights-77679