Why is a united country needed or preferred?

Which statement best evaluates the impact of the 1929 stock market crash on europe? 1. the united states established high export tariffs to europe that reduced goods exported to germany. 2. the united states promoted domestic policy initiates that reduced jobs on american bases in europe. 3. the united states promoted isolationism that withdrew troops from europe causing germany to pay its own national defense. 4. the united states eliminated loans to europe that caused germany to default on its reparation payments to france.