The US is such a small sliver of the world population, as is the west to some extent. ACT scores and such are extremely US centric.
Smartphones were a positive revolution for so much of the world. Consider the hundreds of millions of children (more than the entire US population exclusively used in this argument) growing up in rural poor households surrounded by illiteracy. They suddenly had access to the wider world. They had the opportunity to take initiative in ways they didn't have before. They had access to limitless education, and an easy way to pick up a global language. When kids left the village for a city they could video chat with family instead of going months of no contact.
To some extent, I'm talking about the final leg of the internet revolution, not phones specifically, but in many areas of the world where electricity is intermittent, it was phones that finally drove wider internet penetration.
Are there downsides? Certainly. is smartphone addiction and social media a problem? Research says that it probably is, but for a long time I've felt that the positive impacts on a global scale are being downplayed, especially in the US. Not everyone who gained cell phone connectivity had a PC at home with a steady power supply as a baseline, and schools stocked with computers. We have a huge wave of new people growing up who had access to far more information than the previous generation. If I'm going to make a casual, broad-sweeping generalization of impact, I'll hazard to guess that the positive impact is being greatly underappreciated globally.