The best possible chance would be a German-Russian-Austrian alliance fighting a British-French-American alliance. If the Germans quickly defeated France in 1914-early 1915 and put some puppet state into power (unlikely), they would dominate the continent and be able to survive a blockade. Have the Americans join in late 1915 over some incident and you have two alliances which can sustain a war with each other and could not be realistically invaded. However, I imagine that both sides would come to a truce as there would be little they could do to hurt each other and the lack of trade would incentivize a peace. You would have to find some way to make the British/Americans find the war worth continuing.
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