While US markets have recently outperformed international markets, international index funds have historically had periods of outperformance (e.g., 1980s, 2000s) and this trend could repeat.
"over the last 10 years International index funds like this have remained fairly flat and as of now the U.S market is on a roll outperforming just about every other Market out there but always remember that is never guaranteed to happen throughout history there have been multiple times where International index funds have outperformed the United States like throughout the 1980s and 2000s and there's certainly the chance of that happening again"