What went wrong on 9/11 with the extraterrestrial technology used to destroy the twin towers, that it caused damage to quite distant objects, such as many cars at separate locations up to a half a mile away?

This was, in fact, human error as it was done by members of the Mercenary Army Program attempting to use the alien technology, in effect, taking a turn to impulse energy. Keep in mind, not only the Twin Towers were destroyed, but the other buildings among the World Trade Center Complex. So with multiple targets over a period of many hours in the aftermath, during which there were fires present, there were many opportunities for hands-on practice and demonstration of capability by humans taking part in the operation. This was done quite well in general, but there were a few miscues causing the energy to stray and become directed at more distant locations for a time, causing strange fires and melting of vehicle components in odd configurations. Keep in mind that there was little risk, as demonstrated by the occurrence of these freak phenomena because they were completely ignored by the world at large, given the power and capability of the Extraterrestrial Alliance to maintain a cover-up through mind control manipulation.