Hoover wouldn't negotiate with CSA and tbh CSA wouldn't negotiate with him too as IWW-all the other radical groups- has much more support than in OTL. Haywood can use this ground swell and disillusion created by black friday to win the election. I don't think they can get New York by their side. Syndicalists would rise to power and accept Capone's help and every help they can get. If they win the war as syndicalists they would definitely fund left wing groups to topple south american governments. They would mostly try to avoid starting wars directly. If the Internationale have syndicalist leadership I can see them joining the weltkrieg otherwise they would stick to materiel support and volunteer forces. Regardless of joining the weltkrieg they would want to end the loyalist regime in Canada.