Is Poland still successfully holding NATO’s eastern flank?
Yes. You are correct Poland.
And they have a lingering dispute over a part of Ukraine (once occupied by Polish for many years) that was grafted to one of the border changes related to the Polish/Ukraine division).
Poland, in my opinion is one of the best and most loyal NATO members. They show continuing loyalty to the USA and we have common past with Poland since the American Revolution.
Unfortunately the EU is controlled by Germany. And they don’t play fair with other EU members. They (Germany) do not believe in fair elections or even freedom of speech. (NAZI traits) And Germany within NATO and the EU are playing the Ukraine card, and loosing. Arrogance before the fall.