Alien Rubicon

An alien spacecraft lands in the ocean just off the coast of New York and effortlessly destroys everything in the area without moving. The military investigates as the spacecraft heads inland, destroying everything around it with ease. We figure out that it's a probe, sent expressly to let us throw everything we've got at it while it heads directly for Washington D.C. If it reaches our Capital, it'll destroy it and send a signal to the rest of their species to come down and destroy the rest of the planet. Everything we throw at the ship fails, and it's up to our scientists and military to figure out how to stop the unstoppable before it's too late.