Can wing sweep decrease total drag force at low-subsonic speeds?
Sweeping back a wing of fixed spar length and area does decrease form drag. However due to both its lower aspect ratio (span/chord) and sideways flow effects, it increases induced drag and decreases lift, so that the net L/D ratio or efficiency of the wing falls.
Whether the absolute amount of drag goes up or down depends on other factors, such as wing loading and angle of incidence. In most situations drag would be higher. Where it is less, other design optimisations such as reduced spar length would offer greater improvement.