A Republican congressman misstated his military rank — in a letter that attacked Minnesota Gov. Tim Walz for doing exactly that. Rep. Ronny Jackson (R-TX) was one of a number of signatories to a letter that took issue with Walz, the running mate of Vice President Kamala Harris, referring to himself at one point as a “retired Command Sergeant Major.” Walz did hold this rank near the end of his 24 years of service in the Army National Guard, but for procedural reasons he did not retain the rank when he retired — a technicality that his counterpart on the Trump ticket, Ohio Sen. J.D. Vance, has b…