This study will enroll participants with urothelial cancer (UC). UC can include cancer of the bladder, kidney, or the tubes that carry pee through the body (ureter, urethra). This study will try to find out if the drugs disitamab vedotin with pembrolizumab works better than platinum-containing chemotherapy to treat patients with UC. This study will also test what side effects happen when participants take these drugs together. A side effect is anything a drug does to the body besides treating the disease. Participants in this study will have cancer that has spread through the body (metastatic) or spread near where it started (locally advanced). In this study, there are 2 different groups. Participants will be assigned to a group randomly. Participants in the disitamab vedotin arm will get the study drug disitamab vedotin once every two weeks and pembrolizumab once every 6 weeks. Participants in the standard of care arm will get gemcitabine once a week for 2 weeks with either cisplatin or carboplatin once every 3 weeks.