There are missions all over the world, so they are not tied to one continent. There are various missions in the United States, but also in Europe and China. From the hub you choose which mission you want to get started with, unfortunately you cannot fly or walk around the world freely. Marvel’s Avengers is a story-driven game, and each mission deepens one or more of the characters.
The voicecast of the Marvel’s Avengers is certainly not wrong. Some well-known names are Troy Baker as the Hulk (Joel The Last of Us), Nolan North as Tony Stark (Nathan Drake Uncharted). If you’re a fan of Critical Role, you might recognize Laura Bailey as Natasha Romanoff (Abby The Last of Us Part 2) and Travis Willingham (Roy Mustang Full Metal Alchemist) as Thor by the voices.