The war materials they were giving to the Whites to help them fight the civil war. This isn't controversial, the US openly backed the Whites in the war.
Did you read that Wiki article? War materials were given to support Tsarist Russia in WW1.
That was the original reason for sending supplies to Russia and it had been going on for years. This expedition was after the fall of the Tzarists government, after Russia had exited WWI, and started months before the armistice.
And again, this is not all the actions taken by America in the conflict.
What was the original reason? Sending supplies to Whites when there was no Whites?
Supplying Tzarists Russia started in like 1914. By the time being discussed, they were supplying the Whites.