Correct, US based OTA DTV is MPEG2 based. ATSC-2 standard includes support for H.264 (MPEG4 AVC), but it isn't in use anywhere yet. Bitrate in the US is 19.4mbit, though many channels will divide this up for multiple streams, (IE, the whole 13.1, 13.2 13.3 sub channel setup) when they aren't using all the bandwidth on the main channel.

My earlier Voom comment came from their high quality over satellite. I made the switch to them from Dish back in 2005, and the difference was pretty amazing. Around the time of shutdown, Voom was working to convert everything over to H.264 to be able to recompress the incoming feeds without introducing visible artifacts, thus allowing them to add more channels. Having just a few months of Voom was enough to make me not want to go back to a provider that recompresses everything to the point of artifacting.