Poland had an army which could put up initial resistance and save time to build up better defences.
I cant agree with you, you underestimate psychological impact Swedish invasion had on morale of Polish population. Since XV century until 1655 not a single enemy soldier entered Polish mainlands! All wars were fought at borderlands - Pomerania, Prussia, Livonia, southern border, eastern border or at enemy territory. Most of this war were succesful for us. Now lets think about political and military position of Poland n 1655:
- all armies are on the east
- civil war against cossacs and then against Russians lasts for 7 years. In 1654 Russia invaded Poland with army of ~100 000 soldiers.
- Polish nobility had to to pay additional taxes for massive armies and serve in military
- i mentioned Battle of Batoh 1652 and POW killing. Just three years before Swedish invasion, due to commanders failure Poland lost all best units, officer corps, experienced and well-trained soldiers.
I'm not suprised we couldnt fight back in 1655. However after Poland re-deployed its armies it took less than two years to drive Swedes back(despite Brandenburgia and Transilvania invasions in 1655 and1656), in 1657 Poland was even able to send expeditionary corps to aid Denmark in war against Sweden but still - Poland was ruined and depopulated.