An attack on Poland would immediately invoke NATO Article 5, drawing in the combined forces of continental Europe, the UK, the US and Turkey. The world wouldn't need to worry about it going nuclear, conventional forces would have the Russians back over the Belarusian border by lunchtime.
Gammelfisch said it better than I could, but what makes you think Trump would feel any type of responsibility to follow through with a treaty signed by a president that isn't him and was almost 100 years ago?
Probably couldn’t trust Trump to come through, but you have to keep in mind that he’s not an autocrat quite yet. Not everyone in the US government shares his views on NATO and the commitments the US has pledged to under that alliance. Look at the rest of NATO. You have four of the top ten military powers in the world to start off with (UK, France, Turkey, Italy). Then add to that the rest of Europe and Poland’s own considerable military might. Canada would also join in, and those otherwise peaceful Canadians go fucking nuts when provoked. Even disregarding NATO, you have the Anglo-Polish Alliance, which is a mutual assurance that the UK provides military assistance (or vice versa) if their ally is invaded. Poland also has many close friends and allies in the old East Bloc, so the misconception that they would be left to their own devices is simply untrue.
Mango Fucking Mussolini would abandon Poland like the British and French in 1939. Fuck Russia and the MAGAts, this German supports the European NATO members and especially our neighbors to the east. If the motherfucking Muscovites attack, I will request to be reinstated and do whatever I can to stop the filthy bastards.
Who needs’em? If Uncle Vlad hears that Ze Germans are rolling across the Polish border, he’ll be skipping on one leg back to Russia while changing his soiled pants. :D
This is what I fear will happen when Canada is annexed. The other NATO members will express outrage, but who's going to launch an invasion across the Atlantic against the most powerful armed forces in the world to liberate Canada?