GATE: Thus the Shattered America Fought there

It's been 40 years since the second american civil war and world war III, Exposing the russian president and generals responsible for nuking the capital of Washington D.C. after starting the second american civil war. The US started to recovering and fix their economy bits by bits. They're even build their advance and powerful technology for the military. But anything chances when the gate open on new york city. When roman army attack them. But they're were repelled by the USRAF. They're decided to send their military to the other side. However, They're will soon meet the JSDF from alnus hill. How will the JSDF react to the future USA? Also how the world react to an about the alternate second american civil war?

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Crossover: GATE: Thus JSDF Fought there X Shattered Union