The Germans sent Lenin back to Russia ten days after U.S. entry into WW1. Does anyone know of primary source evidence that the Germans thought of Lenin as a possible way to counter U.S. entry by removing the Russians from the war?
It takes time for such operations to be planned, organized, and carried out; it is unthinkable that it could have been done in few days. Moreover, it made an eminent sense for the Germans to send the Russian Boleshevik exiles back to Russia regardless of any US policy.
See the answer to another recent question for more details.