And herein lies the world of difference between the First World and the
Outbound passport control in Poland is a function of the state Border
Guards, who may at any time disallow your exit, until such time as you
jump through such hoops as the Polish Government may demand.
(For example, until you get a Polish passport, if the Polish Government
arbitrarily decrees they will let you out only on a Polish passport;
presumably also until you grow a beard, should the Polish Government
decide that all travellers must wear a beard).
Outbound passport check by an airline in the US or Canada is designed to
verify your admissibility at destination, in order to protect the
airline company against the trouble and expense of flying you back
free of charge (under the International Civil Aviation Organization
inadmissible passenegr rules) to wherever you came from. The US
Government would not dream of impeding your exit unless there is a court
order or an arrest warrant against you.
The difference between the rule of law in the US and the authoritarian
state rule in Poland is in the practical enjoyment of your
theoretically guaranteed rights. While no one would dream of depriving
you of your freedom of movement in the US, a Polish border guard may
demand just about anything from you, and your recourse against such
actions is extremely limited in practice.
So, if you are a Polish-American travelling on an American passport, you
might not be let out of Poland despite being clearly admissible to the
United States. The Polish Government, in its infinite wisdom, believes
that you should have paid them handsomely for the issue of a Polish
passport and reserves the right to punish you for not doing so. Since
its their sovereign territory, they can do what they like. So can
Guinea-Bissau, Congo, Liberia, Sierra Leone, North Korea, Libia, Syria,
Iraq and many other places where no sane person goes, unless they have
an extremely pressing reason to do so.