For US investors with int'l index funds (stocks or bonds) in their investment portfolios, have they generally done better than US index funds? I'm here wondering whether to add international index stock or bond funds when the US appears to outdo them. Also even if US markets do crash, the greater likelihood is that int'l ones will too so not too sure about the 'avoiding a bad US performance' argument either.
International has historically underperformed US indices. If you want to chase performance and hold no international, then that's your choice. There are plenty of threads here and on the Bogleheads forum (IMO those are much more valuable than the ones here) debating the topic.
The merits of international diversification isn't that the international equities won't feel a US crash. Correlations increase during a bear market and both US and International equities will be hurt. Instead, the benefit is the opposite; during bull markets correlations get lower and you don't want to be holding only equities in the one market that didn't go up. Think of Japan and the lossed decade, not 2008.
https://www.msci.com/emerging-markets Look at this index.....not good, not good at all. This is mainly comprised of overseas companies.