The answer to this question can vary dramatically based upon the definition of the terms used, as well as the fact that our statistical data has not been and never will be exact. In order to give you an answer, I'm going to define "survival" as not being killed in the war, and I will define "chances" as the percent of military personnel killed divided by the peak size of the military for that country. Obviously there is nothing exact about this method, but it at least gives a general idea of the attrition each country's military endured.
US Population in 1939: 131,000,000
Peak Military Strength: 12,000,000
US Military Deaths: 407,000
National Chance of Casualty: .003%
American Military Chance of Casualty: .033%
British Population in 1939: 47,000,000
Peak Military Strength: 4,700,000
UK Military Deaths: 383,000
Casualties as percentage of population: .008%
British Military Chance of Casualty: .08%
German Population in 1939: 69,000,000
Peak Military Strength: 10,000,000
German Military Deaths: 5,000,000
Casualties as percentage of population: .07%
Germany Military Chance of Casualty: 50%
Soviet Population in 1939: 168,000,000
Peak Military Strength: 12,000,000
Soviet Military Deaths: 10,000,000
Casualties as percentage of population: 5.9%
Soviet Military Chance of Casualty: 83%
As a general conclusion, the American soldier would be most likely to survive, followed closely by the British soldier. The German and Soviet soldiers' prospects are much more grim. Please note that the figures given does NOT mean 50% of German soldiers and 83% of Soviet soldiers would die, so use it as a guide instead of a rule.