Tableau can draw a map from any field with a geographic role: the globe icon next to State and City in the Data pane. Double-click State and Tableau builds the map for you: Longitude (generated) on Columns, Latitude (generated) on Rows and State on Detail. Each state is a mark, and with the Automatic mark type, a state-level map is a filled map: every state is shaded.
Drop a measure on Color to shade the states by it. Choose that measure with care. A filled map of total sales mostly shows where the customers are: big markets always look dark. To compare places fairly, map a ratio or an average, like profit ratio or sales per customer.
Only fields with a geographic role can be placed. Region has none: it's a list of names Tableau can't locate. To see regions on a map, map the states and color them by Region.