Bob,
I would suggest rather than individuals sending off a letter.. Classes vote for a resolution that in effect gives a "vote of no confidence" in US sailing's ability to provide leadership, handle, promote or market catamaran sailing in USA and or dependencies.

Understanding that it will need to be a vote taken according to your constitutions.

This can then be forwarded to ISAF directly with a "CC" to US sailing asking for ISAF intervention and seeking an alternative to US sailing in USA. I would not send directly to US sailing, and there may be merit in only sending to ISAF and letting them contact US sailing..
Secondarily to this is "national" Cat classes could also send voted no confidence motions. These could also be sent to ISAF asking for leadership in setting up an alternative avenue for saling in USA.

This strategy coming from all "International" Cat classes with arms in USA may be noticed more. If nothing is received from ISAF itself then "upping the ante", one can proceed by the "International" classes for a direct no confidence motion against ISAF itself.

Stewart