  Anisotropic transport properties have been assessed in a number of cuprate
superconductors, providing evidence for a nematic state. Here, we analyze
recent experimental data for ultrathin YBa$_2$Cu$_3$O$_{7-x}$ (YBCO) films,
where nematicity is induced via strain engineering, leading to a suppression of
charge density wave scattering along the orthorhombic a-axis and a concomitant
enhancement of strange metal behavior along the b-axis. It is shown that the
anisotropic properties strongly depend on the substrate, which we characterize
by atomic force microscopy (AFM). Based on the AFM data, we provide a
microscopic model that can account for the absence (presence) of nematicity and
the resulting transport properties in films grown on SrTiO$_3$ (MgO)
substrates.

Superconductivity;Materials Science;Strongly Correlated Electrons