Hey ma0,
I did put quite some effort into the US Witholding taxation issue. please cosult this thread
from what you can read there, you will find the general principle of witholding taxes everywhere: the counties of domicile of a fund and it’s underlyings usually witholds a certain percentage. US 30%, CH 35%, IE 0%. for the combination of US domiciled assets and Swiss resident, the 30% can be lowered to 15%