Complex sentence: Matthews helped lead Team USA to gold at the U18s in 2014 and 2015, while leading the tournament in scoring and being named MVP in 2015, as well as earning the top forward slot on the Media All-Star team.
Split into simpler sentences: Matthews helped lead Team USA to gold at the U18s in 2014. He did so again in 2015, this leading the tournament in scoring and being named MVP in 2015, as well as earning the top forward slot on the Media All-Star team.