Former Castleford coach Terry Matterson will take charge of the United States side during the World Cup later this year.
The 46-year-old Australian stepped in to the vacancy left by Brian Smith, who stepped down on Thursday because of a pressing family engagement.
Matterson, who is currently assistant coach at North Queensland Cowboys, is the Tomahawks' third head coach in two months after former Bradford boss Matthew Elliott stepped down in August to concentrate on his duties with New Zealand Warriors.
"This is a really good opportunity and I know how good the experience was for Matt Elliott," said Matterson, who was in charge of Castleford for six seasons between 2006 and 2011.
"This will be a fantastic chance for myself and the players in helping to spread the gospel of rugby league and perhaps even shock a few people. I'm thrilled to accept the job."
The Tomahawks are due to play a warm-up match against France in Toulouse on October 18, before taking on the Cook Islands in the first of their three World Cup group matches on October 30.
Former Hull player Clint Newton and ex-Castleford utility back Ryan McGoldrick, who was released by Salford on Thursday, are among the names in Matterson's squad.
Parramatta player Joseph Paulo will captain the side, while his brother Junior has also been named in the squad which contains 10 players born in America.
USA: Mark Cantoni (Dalby), Andrew Durutalo (USA Eagles), Bureta Faraimo (Mackay Cutters), Gabriel Farley (Southampton Dragons), Kristian Freed (Connecticut Wildcats), Mike Garvey (Ipswich Jets), Roman Hifo (Mangere East Hawks, New Zealand), Danny Howard (Wentworthville), Stephen Howard (Tuggeranong Vikings), Luke Hume (New York Knights), Judah Lavulo (Cabramatta), Joel Luani (Wests Tigers), David Marando (Belrose), Ryan McGoldrick (Salford), Clint Newton (Penrith), Mark Offerdahl (Connecticut Wildcats), Joseph Paulo (Parramatta, capt), Junior Paulo (Parramatta), Craig Priestly (Southampton Dragons), Matt Petersen (Cudgen Hornets), Tui Samoa (Redcliffe Dolphins), Matt Shipway (Newcastle), Les Soloai, Lelauloto Tagaloa (Hawaii Chiefs).