How did Woodard Wilson violated his neutrality?

Many believe he violated the neutrality of the United States by aiding the Allies of WWI by openly sending supplies, medicine and arms to the allied nations of WWI. Woodrow Wilson stated that this was simple trade, and to a certain extent it was, however the problem with this was that it openly showed that the United States favored the Allies over the Central Powers. The United States however never showed any act of war, or started any act of war. The argument of Germany and the other Central Powers was that by trading with the Allies and by sending arms that that was an act of war, yet, they were never physically attacked by the United States. The citizens of the US were attacked by German U boats, and the Zimmerman Telegram incited Mexico to attack the US. The problem was not with Wilson, but with the setup of WWI, the US was isolationist until the point of attack and pressure by Germany and the Central Powers, but this was somewhat started by Wilson sending aid to the Allies, though not at all a breach of neutrality, the US sent aid to Afghanistan during the USSR invasion, and did not breach neutrality according to UN and International Law, and China technically did not breach neutrality when sending arms to the Viet Cong during the war in Vietnam. Neutrality is greatly considered not attacking another nation, but one may wish that another wins or loses, according to foreign policy, to a certain extent.