There are numerous stories about chop suey's American origins, but (according to Wikipedia) "there is no good evidence for any of these stories."
Several sources in fact agree that a dish called chop suey (or chap sui, or tsap seui) was known in China as long ago as the 16th century. According to foodandwine.com the name means "miscellaneous leftovers"; Wikipedia reports that it was made with offal. But History Today provides what is arguably the most telling appraisal: "A dish [chop suey] which arrived with the Gold Rush, spread with the railway and endured prohibition was Chinese by origin, but claimed by America."
© Haydn Thompson 2022