There are no "optics" to Mbereko playing. Full stop. He plays a niche sport in America at a level that doesn't even register for anyone but a small group of diehard hockey fans. Barely anyone knows who he is and only a slightly larger group cares about the WJC. There is nothing to gain from playing him because of "optics" and it's gross to suggest that's the case without any evidence.
The reality is he got an opportunity in the 2022 WJC because the starter (Drew Commesso) withdrew from the team and the backup (Dylan Silverstein) wasn't available due to a long-standing medical issue that completely derailed his career. He got an opportunity in the 2023 WJC because the likely starter (Silverstein) was still out, the 2003 American goalie class is extremely poor where Mbereko is the best of that age group with a lot of USAH / international experience, he's having his first respectable junior season with Colorado College, and the best goalie on the team is only 17 in a tournament that typically leans heavily on 19 year olds.
He's had an opportunity due to a lack of goalie depth combined with injury and withdrawal, nothing more, nothing less. If he was a white dude named John Smith with the same resume, he still would have had the same opportunity given the same circumstances.