Transaction Rollback on DROP DATABASE
There are several SQL statements you cannot use ROLLBACK  as MySQL Implicitly Commits those Statements such as:

CREATE / ALTER / DROP DATABASE
CREATE /ALTER / DROP / RENAME / TRUNCATE TABLE
CREATE / DROP INDEX
CREATE / DROP EVENT
CREATE / DROP FUNCTION
CREATE / DROP PROCEDURE

For Such Statements it doesn't matter weather you are using explicit Commit or not the statement will Commit implicitly ass soon as you execute it.