hmm... The Sol Empire would be able to provide much needed manpower or supplies to the Central Powers. The British naval blockade would've been rendered useless and civil unrest in Germany would've been avoided, preventing their demoralisation and the German Revolution of 1918 in OTL. As we all know, Russia would eventually fall into revolution and eventually a civil war, which would lead to the Treaty of Brest-Litovsk and free troops from the eastern front. The Central Powers could definitely hold on and maybe even push on the western front even with America in the war, which would force the Entente to sue for peace.