<<One possibility one might consider having a look at is one of the funds that tracks the "MSCI World EX-US Equal Weight Index".
I can't find a fund in the US (ETF or mutual) that tracks it, but there are several in Europe. One ETF is IE000OEF25S1 from Invesco. I find conflicting information on line, but a US person may be able to buy a UCITS ETF. (a registered European fund).>>

Sounds interesting, but the ETF from Invesco that you suggest is not “ex USA” and unfortunately I can't find any other ETF that tracks the “MSCI World Ex-USA Equal Weight Index” (UCITS would be suitable for me as a European anyway).

Yes, I couldn't find an ETF using the MSCI World EX-US Equal Weight Index, either.

The World equal weight is interesting, though, as a one-fund solution:

MWEQ Invesco MSCI World Equal Weight UCITS ETF Acc
invesco.com - Invesco msci world equal weight ucits ETF acc

United States
39,22%
Japan
14,57%
Canada
6,17%
United Kingdom
5,63%
France
4,33%
Germany
4,06%

Compare to cap-weighted VT Vanguard Total World Stock ETF:
investor.vanguard.com - Investment products

United States
62.70%
Japan
5.80%
United Kingdom
3.50%
China
3.40%
Canada
2.70%
France
2.30%