We investigate the macroscopic effects of charge-density waves (CDW) and superconductivity in layered superconducting systems with broken lattice inversion symmetry (allowing for piezoelectricity) such as two-dimensional transition metal dichalcogenides. We work with the low-temperature time-dependent Ginzburg-Landau theory and study the coupling of lattice distortions and low-energy CDW collective modes to the superconducting order parameter in the presence of electromagnetic fields. We show that superconductivity and piezoelectricity can coexist in these singular metals. Furthermore, our study indicates the nature of the quantum phase transition between a commensurate CDW phase and the stripe phase that has been observed as a function of applied pressure.6914