Final answer:
The U.S. embassy reopened in Havana in July 2015, marking an important step in the normalization of U.S.-Cuba relations after 54 years.
Step-by-step explanation:
The U.S. embassy that reopened in July 2015 after being closed for 54 years is located in Havana, the capital city of Cuba. This reopening marked a significant step in the re-establishment of diplomatic relations between the United States and Cuba, which had been severed during the Cold War. This normalization of relations was announced in December 2014 by then-President Barack Obama and included the easing of travel restrictions, the review of Cuba's status as a state sponsor of terrorism, and the reinstatement of embassies in their respective capitals.