what problem or social issue was nationalism intended to rectify??

Answer 1

Your question implies that certain persons cooked up nationalism to rectify a problem or social issue. Nationalism was a feeling that welled up in many people in many parts of the world in the 19th century that their "nation," "tribe," or "territory" deserved independence, recognition, and/or expression. These feelings led to ideas that Germany, Italy, Serbia, or Greece should be reunited, if they were separated, or freed, if they were dominated by others. When Italy was united, but without certain territories the Italians felt were rightfully their's, there grew an idea of Italia irredenta--unredeemed Italy.