Was the us neutral in WW1?

No.

The Great War, as it was called then, started in Europe in the summer of 1914 and remained primarily a European war for its duration. By 1915, however, the German practice of unrestricted submarine warfare had been established in the waters surrounding England. Over the next two years, this practice resulted in the sinking of more than half a dozen US ships bound for England, and especially the passenger liner Lusitania, with the loss of nearly 1,200 civilian passengers.

In April 1917, the US declared war on Germany and its allies. When the war ended a year and a half later, the US was one of the victors, alongside Great Britain, France, and others.