he French army was not demoralized when the time came to fight. They were able to give a good account of themselves in virtually every battle despite a number of shortcomings, General Lescanne managed to make it from the battle of France, to the armistice undefeated in battle! Even then he refused to be taken into captivity. In fact, there were numerous pockets of resistance when France had officially surrendered, these pockets were not easily closed either.Don't know guys, the French Army was highly demoralized, lacked fighting experience(something which the Poles had) and overall ruled themselves by an outdated form of warfare.
Their failure was in strategy and later, betrayal by the political classes. Not in moral or experience, or indeed thelower levels of command.
Poland's defensive line was compromised early, a stalemate was not going to happen given that they tried to fight the Germans at the border rather than on preferable terrain. If they had done that however, they may have slowed the Germans down a few weeks, it would only take one succesful envelopment (and believe me, the Germans had the know-how, ability and time) to get the ball rolling again, past the defensive lines and onto the rest of Poland. Afterall, Poland was just as liable to fall victim to what ultimately got France (having no strategy to ward off the schwerpunkt)It was very clear that the poles were not going to throw back the German Armies all by themselves, but without the Russian backstabbing there were lots of chances of a stalemate that helped the western allies to send support and troops as soon as possible. After all, the Baltic was not closed up until the fall of Norway.
Even at a glance, the Poles are hopelessly outnumbered and outdone in terms of technology. The fight they put up was amazing as it is, it's too much to ask of them to stop the entire German army (except the token force on the Rhine)
The Western allies would have kept all their troops in France, Soviets or not: France would be more protected, the infrastructure would be better, it would be closer to Britain. Most importantly, the French army was already there! (Not that putting allied troops in Poland would have stopped the Germans anyway)
It really is hard to over-emphasise how much of an advantage the blitzkrieg doctrine gave the Germans over everyone else (... That they could get to by land...)