Tax on dividends - US stocks

Hello, I already asked this question in another thread but it got lost in the comments so I’ll see if I can get a reply here.
As an Italian investor I should be withheld only 15% on US stocks after filing the W8-BEN.
My question is, does that apply to every single stock on the US stock exchange? Or is there any exception?

There are some exceptions. Medtronic (MDT) is Ireland domiciled and I have received dividends minus a 20% withholding tax. I have also received dividends from a Unilever ADR (UL) with no withholding tax. It is treated as income from a UK company. These are both NYSE stocks. The treaty rate for UK-Ireland is 15%, so I can only take a credit for 15% and thus there is some small element of double taxation. This doesn’t really answer your question except to show that there are exceptions to the 15% rule.