https://help.cbp.gov/app/answers/det...plant-products
this part may shed some light, though you don't seem to have propagative plant material so I'd think they may be less of a concern. I've brought in small bits of plants (declared) without issue but it depends on the specifics.
Propagative Plant Material (Plants/Plant Parts for Planting)
Many plants may enter the United States from foreign countries, provided they meet certain entry requirements. Entry requirements vary by plant, but the following requirements universally apply:...
But regardless, just declare it on the customs form. Worst case they'd confiscate the branch pieces; best case they give you the OK and you're good to go.