Answer:
Correct answer is D. It forced Soviet leaders to withdraw troops from Eastern Europe.
Step-by-step explanation:
A is not correct as American troops haven't entered that territory at all.
B is not correct as United States were not able to affect all this changes that much.
C is not correct as there were not wars in Europe, except the one Yugoslavia, which was not even under the influence of Soviet Union.
D is correct because Soviet troops withdrew, and new democratic regimes were established in those countries.