How did unrestricted submarine warfare lead to the u. s involvement in ww1?

Unrestricted submarine warfare was first introduced in World War I in early 1915, when Germany declared the area around the British Isles a war zone, in which all merchant ships, including those from neutral countries, would be attacked by the German navy. German ships would attack no matter who they were

The sinking of the Lusitania. Had precious cardboard aboard and many Americans who lost their lives due to Germans sinking our ships. By using U - Boats. President Wilson, had seen enough for him it was the final straw, he officially sent a declaration to congress to declare war soon afterwards. Well I mean after all we were just trying to remain neutral but it didn’t work out so well.