You don't need a US trust.
The plane mere needs to be continuously owned by a US citizen(s) or by a US corporation.
In the case of the corporation there is a minimum figure on the % shareholding which needs to be by US citizens.
A trust is merely a device whereby the owner owns it on trust for the actual operator, and there is a document signed. You do the same if owned by a corporation.
But you don't need a formal trust document at all. If for example I had a son who was a US citizen, he could own my (N-reg) plane and I just happen to be flying it.
Thank you for that link Mike. It suggests that you can own (non US) an N-reg plane, outside the USA, for up to 6 months. This is complete news to me!!