Shingon was brought to Japan by Kukai at a time when most Tibetans were still yak-herders. Admittedly, Tibetans had their own blazingly effective shamanism -- Bon -- that was later harried and suppressed by "Buddhists."
But although it rises from the same root as what goes by the name Vajrayana, Shingon, unlike Tibetan Tantrism, never succumbed to the fascistic excesses of Guru Yoga under the Tulku system.
All people who care about intelligent human evolution look forward to the return of Bonpo and the dismissal of feudalistic Vajrayana (with the exception of Ati Yoga, which is originally Bonpo in any case!)
Shingon Magic can help you to resist and transform the negative assaults of Vajryanists -- and if you associate with any Buddhists in America right now, you are sure to experience these. But it does more. As Shugendo, it allows you to manifest the primordial Buddha Mahavairocana right here-now as the natural activity of body, speech and mind, so that you can truthfully say:
I have realized that which is unborn;Shingon magic is the True Flower of enlightened Nature itself. Svaha!
It is that which language cannot communicate.
It is free from all defilements;
It transcends causality.
I know that it is void like space.