Absolutely not. I keep seeing this simplification thrown around and it's patently false. The uniform spherical cow analogy works better when saying "consider a

Absolutely not. I keep seeing this simplification thrown around and it's patently false. The uniform spherical cow analogy works better when saying "consider a nation-state as a single actor in a global economy." The rational actor assumption is more along the lines of the continuum approximation in fluid dynamics: that even though we don't have the power to model each individual molecule, we can do well enough by applying heuristics on top of that (pressure, density, etc.) that we can reason out some cause-effect behavior by measuring and tracking those higher-level quantities. We can even derive equations from them, though they may not have analytical solutions. The problem with this is of course not just the inhomogeneity of the environment with respect to these higher-order quantities, but with the molecules themselves. This combined with strong nonlocal effects makes economics a really really difficult science to pin down mathematically, so all we seem to be able to do so far is fit the data to one of a few common models and wipe our hands clean of it.