We discuss the impact of neutral-current parity-violating deep-inelastic scattering (PVDIS) of electrons from protons and deuterons on the determination of the weak mixing angle, $\sin^2{\theta_{\rm W}}$, and parton distribution functions (PDFs) at large parton momentum fractions $x$. Using the JAM global QCD analysis framework, we study the effect of incorporating pseudodata simulated for 11~GeV and 22~GeV Jefferson Lab kinematics, accounting for radiative corrections in a factorized QED+QCD approach and uncertainties from higher-twist corrections in $\gamma Z$ exchange. We find that including future PVDIS pseudodata could yield important constraints on the value of $\sin^2{\theta_{\rm W}}$ at low $Q^2$ and on the high-$x$ behavior of the strange-quark PDF and the $d/u$ PDF ratio. The strong correlation between $\sin^2{\theta_{\rm W}}$ and the $x$ dependence of the PDFs demonstrates the necessity for a simultaneous analysis of QCD and electroweak quantities to ensure an unbiased determination of the weak mixing angle from PVDIS data.