100 years ago you would have probably mostly invested in the UK, French, German and Russian stock market as well as the US. So if you want to predict the next 100 years I would try to combine the performance of the UK and the US, on the assumption that US is going to behave economically like an existing power rather than an up and coming power.
Also, just as some risky "foreign" markets did awesome a hundred years ago-- that's what the US was to the investing world in 1900, and it did great-- some will do great over the next 100 years. Some will have wipe outs as Russia, Germany and Argentina did. The future is hard to know.
Really though, owning some vanguard funds is a good idea. I'd just hold on to a little real estate as well.
If one took the long-term "buy and hold" strategy, there would be no reason not to include Russia in your portfolio, in proportion to its relative market cap.
Of course, "buy and hold" would have been very wrong in that era (two of your superpowers would permanently tank), as it might be in this one.
Also, just as some risky "foreign" markets did awesome a hundred years ago-- that's what the US was to the investing world in 1900, and it did great-- some will do great over the next 100 years. Some will have wipe outs as Russia, Germany and Argentina did. The future is hard to know.
Really though, owning some vanguard funds is a good idea. I'd just hold on to a little real estate as well.