Are the brake cable and linkages across the axle loose?
If not, take out one or more of the clevis pins so that you're sure the brake isn't being pulled on.
Next, is the lever that goes into the wheel cylinder now loose and can you move the cylinder back and forth.
If not it's likely to be the shoes stuck to the drum.
If the engine runs, try driving off and see if it releases, or put it in gear and rock the car.
If still no luck, get the drum off. If the shoes are stuck to the drum, this can be hard work. Try hitting the drum with a heavy, but soft hammer (or a lump of wood).
If you pull the drum off (may well need puller) you may bend the shoes, but if it's stuck togethr badly you're going to be replacing them anyway.