Are both musicians C. J. Ramone and Jessica Jung American?
yes
Title: C. J. Ramone
Passage: Christopher Joseph Ward (born October 8, 1965), better known as C. J. Ramone, is an American musician best known for working as the bassist, backing and occasional lead vocalist of the punk rock group the Ramones from 1989 to 1996.  He is one of the three surviving members of the Ramones, along with two of their drummers Marky Ramone and Richie Ramone.
Title: My Decade
Passage: My Decade is the third extended play by South Korea-based American singer Jessica Jung.  It was released on August 9, 2017, by Coridel Entertainment, and celebrates her 10th anniversary as a singer.  It consists of 6 songs, including the previously released single "It's Spring" and the title track "Summer Storm".
Title: Jessica Jung
Passage: Jessica Jung (born April 18, 1989), known professionally as Jessica, is an American singer, songwriter, actress, model, fashion designer, and businesswoman currently based in South Korea.  Jung was born and raised in San Francisco, California.  At the age of eleven, she was discovered by South Korean entertainment agency S.M. Entertainment and subsequently moved to South Korea.  In 2007, Jung debuted as a member of the South Korean girl group Girls' Generation.  The group later became one of the best-selling artists in South Korea, and one of South Korea's most popular girl groups nationwide and worldwide.
Jessica Jung C. J. Ramone