You do realize that article 5 does not mean that other countries have to join the war, right? They can choose to or they can choose not to. Even if they choose to get involved, it can be in form of economic support. And even if they choose to declare war, it can be in form of loud words. So I expect Poland would be on it's own.
It means they have to under their treaty obligations. If they choose not to, they are in violation of the treaty and NATO is just over. If the Americans want to do this, they should forever be reminded that article 5 has been used only once before, by them, and the allies came to their aid no questions asked.
They are under an obligation to decide what they want to do collectively. If they decide that it was an aggression, then they are under obligation to provide support. It can be exact same"support" that Europe is already providing to Ukraine. That's too say not much of it
The Article 5 wording is vague. It states that an attack against one member “shall be considered an attack against them all.” What is quoted less often is that each member state only has an obligation to take “such action as it deems necessary, including the use of armed force.”