Obviously there is no right answer. One possibility would be to take world weighting as a model. See Vanguard VWRL.
But if you had had a higher weight in US you would have done better last year. It you had higher weight in emerging markets you would have done better this year to date.
My portfolio presently has this
It is overweight in US and UK. I have recently been buying emerging market ETFs, but am not too worried that my regional weights don’t match the world ones in VWRL. I think @Finki once made the interesting point that ETFs in non US regions behave sort of like bonds - long term reliable, but nothing too exciting. I have found that. My VERX and VJPN are fine, up 50% over 7 years, but not doing as good as my Apple stock.
If ETFs are your way of investing you could just buy a world fund like VWRL, SWDA or SUWS. I have many individual US stocks, but cover all other regions with ETFs and managed funds like Fundsmith (cost 0.95%). The overall costs for my portfolio average out at around 0.20% pa. I use ISF, VUKE, VERX, VJPN, VAPX, VFEM, EUE, EMIM, SUWS, and have recently chosen some small positions in ESG funds like EEDM.
People have tendancy to prefer their home market because the stocks are names they know. The popular Vanguard Lifestrategy 100% is around 20% UK, whereas UK is really only about 5% of world market. It is more tax efficient to own US stocks directly than in an ETF like VUSA because of the unavoidable double taxation of dividends that applies to ETF ownership. I have more invested in each of MSFT, PG, AAPL, JNJ than I do in Japan plus Asia ETFs.