They already help. The US delivers weapons and systems since 2018, including missiles like Javelin. US military trainers are there since 2015.
But:
according to media reports from that year the Americans also learn from the Ukrainians as well, since the Ukrainians have combat experience with a conventional, highly advanced, technologically well equipped traditional military enemy being fought at close range on the ground that the Americans have not had in their recent adventures in the ME. Its russian doctrines and Russian drilled troops, no militias, rebels or underequipped part-time volunteers. And its Russian drones and precise artillery bombardment that the American trainers have been exposed to. New experiences, nothing known from Iraq or Afghanistan. This enemy can bite back - in strength. Americna trainers form that tiem said the expriences with the nUkrainians showed taiught them about a growing systematic ground combat competence deficit in the American military.
For example this Austrian polit magazine from 2015:
https://translate.google.com/transla...-lernen-konnen