Scanning tunneling microscopy has been used to characterize the electronic and structural effects of oxygen doping in ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{\mathit{x}}$ materials. Bias-voltage-dependent images of oxygen-deficient nonsuperconducting crystals show that reversible oxygen loss leads to nonperiodic variations in the electronic states near the Fermi level (\ifmmode\pm\else\textpm\fi{}300 mV). Variations in the electronic states near the Fermi level are not observed, however, in images of superconducting samples. In addition, high-resolution images of the BiO layer of oxygen-deficient samples do not exhibit vacancies or strongly perturbed sites, but rather appear similar to images of the BiO layer of superconducting crystals. These data indicate that suppression of ${\mathit{T}}_{\mathit{c}}$ in ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{\mathit{x}}$ may not be due to oxygen loss from the BiO layer.