are you trying to access 2 db's or two tables?
if it is db's then you need to open seperate links to each.
if it is 2 tables then
SELECT * FROM regions as db1, user as db2 WHERE db1.region_leaders_forum_username = '$us' AND db2.username = '$us' AND db2.password = 'hihih';
you may also want to use something like this
SELECT db1.region_leaders_forum_username as region_leaders_forum_username, db2.username as username, db2.password as password FROM regions as db1, user as db2 WHERE db1.region_leaders_forum_username = '$us' AND db2.username = '$us' AND db2.password = 'hihih';