I have read that around 23% of the USA sailboat builders went out of business since 2004-2005. I believe 2011 is the latest year for reliable figures, but the total number of cruising sailboats built in the USA was only 622: 30-35 feet = 215; 36-45 feet = 348; 46+ feet = 59. More information here.
I suspect there is a list of all boat manufacturers someplace, but not sure where. If you go here
, and search on sailboat manufacturers you only get 13, and I'm not sure all of them make boats in North America.