Who is responsible for the Cold War?Were the Soviets responding to American aggression, or was America responding to Soviet expansion?

Given these two options, America was clearly responding to
Soviet expansion.  At the start of the Cold War, there was really not any American
aggression going on.  The US had not made any moves that were directly hostile to the
Soviet Union.  By contrast, the Soviets had taken control over all of Eastern Europe and
were clearly trying to impose communism on those
countries.

However, I would argue that the Soviets were
responding to something -- they were responding to Russian history.  So it's not as if
they were simply being aggressive and wanting to expand.  The Soviet Union had good
reason to want buffers with the West.  Their country had been invaded (and almost
conquered) both by Napoleon in the 1800s and by Hitler in WWII.  Because of this, there
was ample reason for them to want friendly countries around
them.

Overall, then, I would argue that the Cold War was
started by America's (understandable) reaction to Soviet expansion which was itself a
(understandable) reaction to what had happened to Russia in the
past.