No reported problems,

just a suggestion. Austrians can't get a scond one anyway? And your passport must so full of exotic stamps and visas that it would take the CBP guy quite a while to spot the TUN stamp
I've got one german passport just for NAFTA to keep it 'clean' of the ROW after receiving a secondary in ORD a few years ago due to various UAE stamps in my passport
PS: since when are you flying from TUN? I heard you are a CAS native...