How do I renew my US passport without losing my still valid visas?
New passport does not invalidate old Visa. Visa is valid till the end date of the Visa but if the passport on which visa is stamped has expired, you must get a new passport and then carry both passport for traveling. By the way which country Visas are you talking about? USA has a visa waiver for majority of the nations (184 countries). To many excluded countries, there is Visa on arrival at the immigration desk. Work visa is different. But then again visa validity + latest passport validity dates - whichever expires earlier is the last entry date.