New legislation took effect on Oct 13, 2018, supported by the Outdoor Industry Association, that lowers duties on some footwear products. Check out the article below, and if you have ideas for what should be introduced in the next round of MTB’s, let OIA know (see bottom of article for contact info).
https://sgbonline.com/new-footwear-legislation-now-in-effect/
The full, new US tariff schedule, is available here. Sections starting at Sec1264 deal with footwear.