You don't have to be American, or ever have lived in the US, to owe US estate tax. US shares, US funds, and US real estate are "US-situs" assets — taxed by the US on a non-resident's death above a strikingly low threshold, at rates near 40%. Most people have never heard of it. See your exposure, and how much of it a non-US-domiciled fund can remove.
The US taxes the estates of non-US persons on their "US-situs" assets — and the threshold above which it applies to a non-domiciliary is strikingly low (long set around $60,000), far below the large exemption US citizens enjoy. US shares and US-domiciled funds count as US-situs even when held in an account outside the US; so does US real estate. The rate climbs toward 40%. It is one of the most common, most expensive surprises in cross-border wealth — and one of the most avoidable.
US company shares (even held abroad), US-domiciled funds/ETFs, US real estate, and US-located tangible property. US bank deposits often do not — but confirm, the rules are technical.
Hold US-market exposure through a non-US-domiciled fund rather than US shares or US funds directly. Same investment exposure; generally not US-situs — so the estate exposure falls away. A non-citizen surviving spouse raises a separate issue (QDOT).
The US-situs estate trap, seen from both sides — the family moving wealth into the US and the non-resident who simply holds US assets — plus the fixes, the QDOT spousal issue, and a companion workbook that maps your whole estate by situs. Get the chapter and the launch notice.