The U.S lost the least land
Poland had the highest population of Jews in the whole of Europe at that time, and consequently lost the most.
Poland (prewar frontiers) lost about 3 million of its 3.3 million Jews.
All contrys have lost matches but China have lost the least.
Finland handed over 8 Jews (refugees from Nazi Germany) to the Nazis. The figure given for Danish Jews killed is usually 161.
They lost their country to the Romans in 37 B.C.E. and were never strong enough to reassert independence prior to 1948 C.E.
Poland (pre-war frontiers) lost about 3 million of its 3.3 million Jews.
Finland
This answer is based on the false assumption that all Jews have lost faith in HaShem. Although some Jews don't believe in HaShem, it's far from the truth to say that this is true for all Jews.
Luxembourg lost the least troops during the First World War.
It depends on the country or time-period, Jews have lost and gained rights numerous times through history. Generally speaking, they gained their rights back through advocacy, but this was not the only way. Please resubmit this question referring specifically to the country and/or time-period in question.
I would have to say Poland. On a percentage basis, Poland lost the greatest population and after the war, Poland was controlled by the Soviet Union. Germany and Japan at least were rebuilt and had a measure of independence. The biggest winner of course was the United States.