The Autumn 1941 issue of Public Opinion Quarterly contains an analysis of public opinion as reflected in newspapers (by James Twohey) and a comprehensive list of opinion polls over the previous few months. Twohey notes that while communists were being blamed for strike activities in early 1941, the criticism of communism by newspaper editorials and letters to the editor abruptly stopped when Hitler invaded the Soviet Union. The strikes didn't stop, but the attribution of them to communists did.

On the subject of US intervention, discussions of it increased after June 22, and the tone of the discussions became more positive, especially regarding convoys and other aid to Britain. However, only 21% of Americans favored sending aid to "Russia" (the phrase used for the USSR in all of the polls mentioned in this post) in the immediate aftermath of Hitler's invasion. On June 28, Americans were asked directly about entering the war against Germany and Italy. Only 24% supported such a move (compared to 21% in May, well within the margin of error of these older polls). Nevertheless, when the question was rephrased as whether the US should enter the war if that was the only way to defeat Germany and Italy, people answered 2:1 in the affirmative for months before Hitler invaded Russia, and 85% agreed that whether they wanted it or not, the US would end up fighting in the European War.

The Winter 1941 issue contained polls after June 1941, so it provides some information on public opinion as Barbarossa progressed. On July 12, the American people were asked which side they wanted to win the Russo-German War. Only 4% picked Germany, while 72% said Russia. The rest either didn't know or thought that it made no difference. A particularly intriguing question was, "If Germany were to offer peace on the basis that she would keep only the territory won from Russia, and give up France, Scandinavia and the other conquered countries, would you favor such a peace?" A majority of Americans said they would oppose such a peace (58% oppose / 34% favor). Still, only 21% supported entering the war as of July 1941 (although there was a gap between elites and the public -- about three-fourths of those listed in Who's Who supported entering the war).

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To summarize: the public was not ready to get involved, but only because they still though Britain would win its war (although fewer than 1 in 4 expected "Russia" to defeat Germany). They were willing to fight to prevent a German victory, however, and certainly seemed to be rooting for the USSR in its war against Germany (e.g. rejecting the peace plan that had Hitler give back all but what he'd taken from the Soviets).