Oracle VARCHAR2 datatype is limited to 4000 bytes.

What is the estimated size of your concatenations?

If it is more than 4000 bytes, you will have to CAST the result into a CLOB object (character large binary object).

In that scenario you will have to read Oracle documentation to see if CONNECT_BY supports CLOB datatype.

Try this first

SELECT

CAST(SUBSTR(SYS_CONNECT_BY_PATH(COUNTRY_NAME,','),2) AS VARCHAR2(4000)) AS TABLE_LIST

FROM ( etc.