How was not neutral? It;'s standard practice for Neutral countries to sell things to belligerents. and other nations were doing so.So to dig deeper into your question; to what degree would that entail US neutrality? Since in truth the United States had not been functioning as a true neutral since about late 1915, that would potentially mean a very different war. The United States was producing specifically for French and British a lot of war materials, and supplying foodstuffs. Had the United States been functioning as a Neutral during that entire period it would have demanded that Britain not interfere with US shipments of food, and non war-essential products to the "Central Powers", this would not have been the war we knew at all. It would have also meant that the United States would not have been producing things like ammunition to the Triple Entente which it had since late 1915.
In the Napoleonic Wars this led to a great deal of hostility and eventually war between the US and Britain. The US has historically defended the neutral rights of shipping.
"true neutral" is not a thing international law or policy.
The US did make demands about the British blockade, but the blockade was mostly legal. Demands have no real effect. The Entente trade was highly profitable. the Central powers trade much less so.
The central powers would have struggled to pay for thinsg in the US and did not have the ability to ship things to Eruope.
The US was quite happy to sell to the Central powers.
It was British shipping shipping things to Entente not US ships generally.
The US has only historically defended the rights of neutral shipping WHILE neutral once at war the US demanded stricter blockade than the British.