USA, Canada /
Notarized note required for US travel with child born in Poland and holding American passport. [7]
His American passport will not be a problem upon return because Americans are entitled to visa free entry to Poland. Him having one Polish parent entitles him to stay in Poland for as long as he wants, but you should take care of some paperwork - perhaps a Polish birth certificate since he was born in Poland to prove that he is Polish as well.
I assume his dad is not travelling and that is why you ask this question.
Regarding the notarized note, in Poland specifically, I never heard of it and nobody that I know heard of it (I am talking about mixed nationality couples). And I travel a lot, quite often with a small child. Since he is leaving Poland with you and you both have American passports I don't think you'll have a problem. If you are still worried, have your husband come with you to the airport and if they say anything tell them the father is physically present and they can ask him.
However in one incident, it happened to my wife when she was flying out of Dubai, UAE, together with my son who was was 9 months old. They asked her to prove she is his mother because they have different last names. Well, as a part of the documents we ALWAYS carry when we travel, we have his birth certificate and our marriage certificate. So she showed them his birth certificate and they said thank you, have a nice trip.
Some countries require notarized & attested written permission from a child's father (by law) in order to allow the mother or other relatives to take the child out of the country. I know for example that Syria applies such a law.