This is a study of perioperative pembrolizumab or enfortumab vedotin in combination with pembrolizumab in participants who are cisplatin-ineligible or decline cisplatin with muscle-invasive bladder cancer (MIBC). The primary hypothesis is that perioperative pembrolizumab plus radical cystectomy (RC) plus pelvic lymph node dissection (PLND) and perioperative enfortumab vedotin in combination with pembrolizumab plus RC+PLND will achieve superior event-free survival (EFS) compared with RC+PLND alone. With Amendment 5, outcome measures for programmed cell death ligand 1 (PD-L1) combined positive score (CPS) were removed. With Amendment 8, the primary outcome measure of pathologic complete response (pCR) rates was changed to a secondary outcome measure.