Although things like yarn are now exempt if they don't contain metallic thread, items made out of yarn for children, i.e., hats, will still have to meet the labelling requirements of the CPSIA in order to sell to the U.S.
You can read more here:
http://www.cpsc.gov/ABOUT/Cpsia/smbus/manufacturers.html#q4As for hats, or any product made with yarn, can be sold, without testing.
"Dyed or undyed textiles (cotton, wool, hemp, nylon, yarn, etc.), including children’s fabric products, such as baby blankets, and non-metallic thread and trim. This does not include products that have rhinestones or other ornaments that may contain lead or that have fasteners with possible lead content (such as buttons, metal snaps, zippers or grommets). "
There is a whole list of stuff that is exempt. That is a relief for me! Although I can't find any info about labelling.