If you, a non-resident alien from a US tax perspective, die owning US-situs assets — directly held US stocks, US-domiciled ETFs, US real estate — your estate is liable for US federal estate tax. The exemption is USD 60,000. Above that, rates progress to 40%.
A USD 1M direct US equity portfolio could face a US estate tax bill north of USD 300,000 before anything passes to your heirs. The India-US treaty does not have an estate-tax article covering this — there is no relief on the way out.