In the U.S., “high treason” isn’t a separate legal term; there’s only Treason, defined in the Constitution (Article III, Sec 3) as levying war against the U.S. or giving aid and comfort to its enemies, requiring two witnesses or a confession for conviction. Punishments under 18 U.S.C. § 2381 include death, imprisonment (min. 5 years), a $10,000 fine, and loss of office, though pardons are possible, with few federal prosecutions ever occurring.