Wearing a black, tucked-in shirt and blue jeans, Blinken, 62, wielded a cherry red Epiphone guitar as he addressed the crowd at Barman Dictat, a renowned speakeasy-style venue in downtown Kyiv.

Blinken then performed “Rockin’ in the Free World” by Neil Young, strumming along on the electric guitar and even singing the chorus. Blinken’s visit comes less than a month after Congress ...