What was the most important way that the USA at the end of 1945 was different from the USA in 1939?

The USA were more so ideologically driven by 1945.

Explanation:

In 1939, the USA and USSR, alongside other powers (ie. Great Britain), were united against a common enemy: Adolf Hitler. This incentivised all countries to put their differences aside and unite against Hitler, in order to end the rule of one of the largest threats of the 20th century. Thus, in 1939, the USA were largely cooperative and cordial.

By 1945, once Hitler and the Nazis’ rule was over, albeit the USA attempted to keep strong ties with countries such as the USSR (seen with US President Roosevelt’s friendship with USSR leader Joseph Stalin), ultimately, USA’s next steps were becoming increasingly dependent on the USA’s ideological differences to that of the USSR, bearing in mind the USA were capitalist and the USSR were communist/ Marxist- Leninist. This is evidenced with Truman (Roosevelt’s successor as US President)’s approach to the USSR at the Potsdam conference from the 17th July- 2nd August 1945.

Hope this helps! :)

d

step-by-step explanation:

look at the x and y axis