Much of this is really just advanced common sense.
Customer trust, which either helps or hurts sales. To some extent, seeing a physical company address builds trust with US customers, and perhaps some trust with other nationalities as well. Seeing an address on the Cayman Islands etc reduces trust -- the customer may quite rightly feel that he's at a disadvantage when it comes to warranty claims, credit card refunds etc.
Outside investment. If you plan to or might have to take on US Angel or Venture Capital financing, having your business registered in a tax heaven is most likely a deal breaker. Investment agreements are fairly complex, so to have a lawyer conduct a comprehensive review of the validity & enforceability of these provisions under the tax heaven laws is damn expensive.
Employee trust. See this from the employee's perspective. If you're a US national who has plenty of employment offers, which job would you rather take: The one were you're a regular employee in a US company governed by laws you already know, or the one were you're a consultant to a company located overseas?
to the extent that a US corp is vastly more convenient at least for the US-based activity & revenue (true?),
Yes, that's true.
why shouldn't it be owned by a Bermuda-based company, or something similar?
That is perfectly possible, many multinational companies do more or less this (but typically don't place headquarters in the Bermudas, but fx Switzerland). But it also brings lots of extra accounting work (due to the international subsidiaries), potential legal issues around taxes (transfer pricing), extra fees to the chartered accountants & lawyers & office staff in multiple countries. And in the end, if the people owning the Bermuda company are US nationals living in the US, they still have to pay US taxes on their income.
My basic advice in this situation remains the same: Don't think about tax planning at first, worry about creating a successful business first. If you're open to changing your location, then move to the area most conducive to getting a company off the ground, i.e. a startup hub.
