If something is smashed or blown to bits, it is broken into a number of pieces. If something falls to bits, it comes apart so that it is in a number of pieces.
She found a pretty yellow jug smashed to bits.
See full dictionary entry for bit
to bits in British English
completely apart
to fall to bits
See full dictionary entry for bit
Examples of 'to bits' in a sentence
to bits
I reckoned it was only dread of Melphalan, his Lord, that had stopped him slicing me to bits.
Pritchard, John NIGHT SISTERS
There was rock under it, and when rock falls on rock, anything delicate in between is ground to bits.