Start a sandbox game in the modern era with unlimited money and no disasters. Now build a few docks and start trade routes with the Russians and Chinese to get a bad relationship with the U.S.A. Once your relationship is bad enough your advisor will notify you that an invasion is imminent.
Now quick build a strong military power (army base, barracks, fortresses, airship carriers etc.) raise their budgets and improve the buildings where possible and now simply withstand the attack.
Strongly recomended making a manual save right before the attack so you can just go back to that save and add military power if needed.