A short story about an American soldier (John Dix?) fighting Chinese in America. At the point of his death (blown up and buried) his body is entered by an alien who becomes trapped then reassembles body over the next months. The new John Dix then becomes a very xenophobic bigoted political leader who is finally shot at a rally, the alien then able to leave the body. What remains on stage are a few mouldering bones.
1 Answer
"From These Ashes . . ." a.k.a. "Entity Trap", a short story by Fredric Brown which was also the answer to the question Alien consciousness 'finds' human soldier, soldier becomes President; first published in Amazing Stories, August 1950, available at the Internet Archive. You may have read it in one of these compilations.
The concrete of the pillbox was still moist. As Johnny Dix peered out of the slit, over the sights of the machine gun, he touched it with his finger and hoped it had hardened enough to stop the bullets of the yellow men.
Johnny Dix was dead. But accident had timed with hair-trigger precision the instant of his death. His mangled body lived.
The nameless entity whom we shall call the Stranger paused in his interplanar swing. He had perceived something that should not have been.
And when, presently, the body of Johnny Dix began to crawl slowly and awkwardly—on one arm and two shattered legs—in the direction the other crawling beings had taken, the Stranger didn't know that he was performing an impossible feat.
On the stage of the Bowl, John Dix, Dictator of North America, stood alone, although uniformed guards occupied all seats immediately around the stage and were scattered elsewhere in the audience. A microphone hung just overhead and a speaker system carried the dictator's voice to the fartjest reaches of the Bowl, and beyond. Robert Welson and the others in the room with him could hear it distinctly.
"THE DAY HAS COME. WE ARE PREPARED. PEOPLE OF AMERICA, I CALL UPON YOU TO RISE IN YOUR WRATH AND STAMP OUT NOW AND FOREVER THE POWER OF THE EVIL COUNTRIES BEYOND THE SEAS."
"The exact manner of his death remains, after all this time, shrouded in mystery. Whether he was killed by a new weapon—destroyed after it had accomplished its purpose—or whether the monstrous thing seen by the throngs in the Bowl was a mere illusion, the trick of a prestidigitator extraordinary, will never be certainly known."