Making the case for international equity allocations

I think they've said this every decade for the last 50 years but international equities have been a loser for US investors... Every time.

And they tell us this time will be different... Every time.

I don't know if the sociological explanation is that you get ripped off because you're an outside or if there is some theorem involving exchange rates and stuff that makes sure international investing is always a scam but I find it a little bothersome that the default choice in my retirement plan allocates to an asset class that I think is certain to underperform.