  We analyze Multi Unit Spectroscopic Explorer observations of nine
low-redshift (z < 0.1) Palomar-Green quasar host galaxies to investigate the
spatial distribution and kinematics of the warm, ionized interstellar medium,
with the goal of searching for and constraining the efficiency of active
galactic nucleus (AGN) feedback. After separating the bright AGN from the
starlight and nebular emission, we use pixel-wise, kpc-scale diagnostics to
determine the underlying excitation mechanism of the line emission, and we
measure the kinematics of the narrow-line region (NLR) to estimate the physical
properties of the ionized outflows. The radial size of the NLR correlates with
the AGN luminosity, reaching scales of $\sim 5\,$kpc and beyond. The geometry
of the NLR is well-represented by a projected biconical structure, suggesting
that the AGN radiation preferably escapes through the ionization cone. We find
enhanced velocity dispersions ($\sim 100\,$km$\,$s$^{-1}$) traced by the
H$\alpha$ emission line in localized zones within the ionization cones.
Interpreting these kinematic features as signatures of interaction between an
AGN-driven ionized gas outflow and the host galaxy interstellar medium, we
derive mass outflow rates of $\sim 0.008-1.6\, M_\odot \,$yr$^{-1}$ and kinetic
injection rates of $\sim 10^{39}-10^{42} \,$erg$\,$s$^{-1}$, which yield
extremely low coupling efficiencies of $\lesssim 10^{-3}$. These findings add
to the growing body of recent observational evidence that AGN feedback is
highly ineffective in the host galaxies of nearby AGNs.
