Button,
the threat of liability litigation and, more to the point, the US Tax "global grab" rules on entities that have a US subsidiary or affiliate make the USA a "no go zone" for many UK organisations, including MSCC.
Sorry and that, but unless and until the US stops trying to take money from anyone or any entity that has a link to the USA it will not change.
We have a US Citizen who is the partner of a LogMog member. She is considering renouncing her US nationality because it costs her so much in Accountancy fees and time.