Theoretical studies of the inclusive electron-nucleus cross section at beam energies up to a few GeV show that, while the region of the quasielastic peak is understood at the quantitative level, the data in the Delta production region are sizably underestimated. We analyze the uncertainty associated with the description of the nucleon structure functions W1 and W2 and its impact on the nuclear cross section. The results of our study suggest that the failure to reproduce the data is to be mostly ascribed to the poor knowledge of the neutron structure functions at low Q2.