Getting the root node is trivial in 10g with CONNECT_BY_ROOT operator. In 9i you can get (albeit less elegantly) to the root node by using SYS_CONNECT_BY_PATH and stripping off everything but the first node - see examples of both below...(this is the bit where you say you have 7.1.6)
Code:
Personal Oracle Database 10g Release 10.1.0.2.0 - Production
With the Partitioning, OLAP and Data Mining options

SCOTT> CREATE TABLE table_name (
  2    parent_region VARCHAR2 (30), 
  3    child_region VARCHAR2 (30));

Table created.

SCOTT> INSERT INTO table_name VALUES ('North America', 'USA');

1 row created.

SCOTT> INSERT INTO table_name VALUES ('USA', 'CALIFORNIA');

1 row created.

SCOTT> INSERT INTO table_name VALUES ('USA', 'CONNECTICUT');

1 row created.

SCOTT> INSERT INTO table_name VALUES ('CALIFORNIA', 'ORANGE COUNTY');

1 row created.

SCOTT> INSERT INTO table_name VALUES ('CONNECTICUT', 'FAIRFIELD COUNTY');

1 row created.

SCOTT> INSERT INTO table_name VALUES ('FAIRFIELD COUNTY', 'NORWALK');

1 row created.

SCOTT> COMMIT;

Commit complete.

SCOTT> SELECT CONNECT_BY_ROOT (parent_region) parent_region, 
  2         child_region
  3  FROM   table_name
  4  CONNECT BY parent_region = PRIOR child_region;

PARENT_REGION                  CHILD_REGION
------------------------------ ------------------------------
CALIFORNIA                     ORANGE COUNTY
CONNECTICUT                    FAIRFIELD COUNTY
CONNECTICUT                    NORWALK
FAIRFIELD COUNTY               NORWALK
North America                  USA
North America                  CALIFORNIA
North America                  ORANGE COUNTY
North America                  CONNECTICUT
North America                  FAIRFIELD COUNTY
North America                  NORWALK
USA                            CALIFORNIA
USA                            ORANGE COUNTY
USA                            CONNECTICUT
USA                            FAIRFIELD COUNTY
USA                            NORWALK

15 rows selected.

SCOTT> SELECT SUBSTR (parent_region, 2, 
  2           INSTR (parent_region, '#', 2) - 2) parent_region, 
  3         child_region
  4  FROM  (SELECT SYS_CONNECT_BY_PATH (
  5                  parent_region, '#') || '#' parent_region, 
  6                child_region
  7         FROM   table_name
  8         CONNECT BY parent_region = PRIOR child_region);

PARENT_REGION                  CHILD_REGION
------------------------------ ------------------------------
CALIFORNIA                     ORANGE COUNTY
CONNECTICUT                    FAIRFIELD COUNTY
CONNECTICUT                    NORWALK
FAIRFIELD COUNTY               NORWALK
North America                  USA
North America                  CALIFORNIA
North America                  ORANGE COUNTY
North America                  CONNECTICUT
North America                  FAIRFIELD COUNTY
North America                  NORWALK
USA                            CALIFORNIA
USA                            ORANGE COUNTY
USA                            CONNECTICUT
USA                            FAIRFIELD COUNTY
USA                            NORWALK

15 rows selected.

SCOTT>