Yes, wood bats need a USA stamp. If you use multi-piece and composite wood bats, they must have the USA Baseball Certification Mark.  Otherwise, for the solid, one-piece wood bats, USA Baseball Certification is not very mandatory. It is a specific type of stamp that you need to look at while you play high school league, minor league, Babe Ruth, AABC, or Dixie Youth.  Later this stamp was replaced with the BPF 1.15 mark that is no longer supported.