i just ran into a medium convoy at AM53 , escorted by one mere VW DD, after i sank it ,i turned to take care of the cargo ships.
I shot all of my torps and when i surfaced to make some shooting practice the neutral (US) ships opened fire on me together with the Brits.
I didn't sink any of the US ships at this patrol and they still considered as neutrals , even when the were shooting at me (some hits too).