It's obvious that the ATSC is the lawful (de jure) standards body since their DTV standard is recognized by the FCC. The ATSC clearly defines all 18 DTV formats...however, their DTV standards document does not clearly define an HDTV standard.
However, the ATSC (who established the DTV standard) defined the HDTV standard, as noted by Goaliebob, as being 1920x1080p, 1920x1080i, or 1280x720p (at various frame rates) as being the only acceptable HDTV formats in their Recommended Practices document. One may argue this not a de jure standard, but the ATSC clearly sets the standards and left little doubt as to their definition of HDTV. Plus, these HDTV formats are certainly the "de facto" standard because they are being deployed by many, if not most, video providers selling HDTV programming.
Additionally, the ATSC HDTV standard made reference to incorporating the ITU-R BT-709-3/1125 recommendations, which define HDTV as 1920x1080 interlace/progressive at various frame-rates...there is no mention of 1440x1080 or 1280x1080. Clearly, the overwhelming amount of evidence does not support the later two formats being called HDTV in any form or fashion. However, if we continue to accept HD-Lite being passed off on us as HDTV, then it may very well become a de facto standard.
1440x1080 and 1280x1080 may be nice TV, but there is no way in hell anyone can logically argue it meets any national/international standard for HDTV...not unless they have a vested interest (agenda) in HD-Lite.
I say write your congressman in addition to the FCC and FTC regarding this fraud being perpetrated upon the American people.
Just wanted to add that pages 94-97 of the ATSC DTV Standard define the role of the Digital HDTV Grand Alliance, their being recognized as the principal supplier of information documenting the advanced television system, the "Grand Alliance" support by the ATSC and other standards organization like the FCC, SMPTE, EIA, IEEE, MPEG, and NCTA. Needless to say, their proposal (attached for your consideration) for Terrestrial HDTV (over-the-air and cable) proposed only two HDTV standards: 1920x1080 (p/i) and 1280x720(p) at various frame rates. Again, there is no mention of 1440x1080 or 1280x1080 (aka HD-Lite).