  We compare mid-infrared (mid-IR), extinction-corrected H$\alpha$, and CO
(2-1) emission at 70--160 pc resolution in the first four PHANGS-JWST targets.
We report correlation strengths, intensity ratios, and power law fits relating
emission in JWST's F770W, F1000W, F1130W, and F2100W bands to CO and H$\alpha$.
At these scales, CO and H$\alpha$ each correlate strongly with mid-IR emission,
and these correlations are each stronger than the one relating CO to H$\alpha$
emission. This reflects that mid-IR emission simultaneously acts as a dust
column density tracer, leading to the good match with the molecular gas-tracing
CO, and as a heating tracer, leading to the good match with the H$\alpha$. By
combining mid-IR, CO, and H$\alpha$ at scales where the overall correlation
between cold gas and star formation begins to break down, we are able to
separate these two effects. We model the mid-IR above $I_\nu = 0.5$~MJy
sr$^{-1}$ at F770W, a cut designed to select regions where the molecular gas
dominates the interstellar medium (ISM) mass. This bright emission can be
described to first order by a model that combines a CO-tracing component and an
H$\alpha$-tracing component. The best-fitting models imply that $\sim 50\%$ of
the mid-IR flux arises from molecular gas heated by the diffuse interstellar
radiation field, with the remaining $\sim 50\%$ associated with bright, dusty
star forming regions. We discuss differences between the F770W, F1000W, F1130W
bands and the continuum dominated F2100W band and suggest next steps for using
the mid-IR as an ISM tracer.
