"Suppose you do business with an American company that has servers in Australia (for the record we are registered in the UK, not the US), and they get a FISA warrant? Of course they will send the info over"
There's a way out. Those server offshore must be handled by subsidiary. Then the parent company in US does not have the data and they can not also command subsidiary to handle it over.
That means the best option is not to use wholely owned subsidiaries and instead have a partnership with the parent owning a large plurality but non-controlling interest (say 10 partners from various countries, with the parent owning 49.9% of the subsidiary). You can set the agenda, more or less run things how you want, but anything you try to do as shareholder can be vetoed by the other 9 acting in unison.
There's a way out. Those server offshore must be handled by subsidiary. Then the parent company in US does not have the data and they can not also command subsidiary to handle it over.