NASA for it's part had a "silent gentleman's agreement" with the Soviet space program to share "responsibilities" and share data collected 1 between each other.

A quote from the same source above shows that NASA put a lot of significance on the landing and the subsequent data (and a lot on the relationship these efforts built):

Because the United States and U.S.S.R. agreed to share the results of NASA’s Pioneer Venus mission in 1978 and the Soviet Venera missions, scientists and space experts on both sides placed enormous symbolic and scientific value on the results of these joint efforts.

This did lead to a bit more cooperation between the two, the same article mentions how the Soviets left Mars alone anticipating getting data from the US mission, and the US focusing on Mars for the same reason.

Scientific American 2 describes how the technology used for the landers and probes used were "quite an achievement". The first probes were crushed by the atmosphere, which in itself provided a lot of data on Venus. The article makes it sound like scientists from all over were excited to know about the dense atmosphere and what impact it has on probes.

So in this regard the missions were not secret and did not cause a large uproar, at least to NASA and other government folks, because of the limited cooperation between the two organizations.

I am not a historian, but I am a history undergraduate student with some experience doing historical research. This topic is pretty far off from my usual topic of interest, but I figured I'd give it a shot. After looking over a few databases, I found some newspaper articles that might interest you on lexisnexis. The one that I think might be most useful comes from the Globe and Mail, not an American newspaper, but still a useful article for your purposes it seems. The link to the article is here if you are interested: http://www.lexisnexis.com/lnacui2api/api/version1/getDocCui?lni=4MBC-V6P0-TXJ2-N0KS&csi=270944,270077,11059,8411&hl=t&hv=t&hnsd=f&hns=t&hgn=t&oc=00240&perma=true

This paragraph seems to suggest that the success of the Venera Programme prompted the U.S. to take a cooperative stance towards the Soviet Union's space exploration programmes:

The spirit of co-operation continued after the Venera mission when two Soviet researchers showed the spectacular color pictures (first ever) from the surface of Venus, and presented preliminary results of a soil sampling experiment to a group of anxious U. S. scientists attending the annual Lunar and Planetary Science Conference at the Johnson Space Centre in Houston.

It isnt a whole lot, but hopefully it is a good jumping off point. I saw a number of other articles on lexisnexis that might be useful (I had a total of 482 hits for the search phrases "venus" or "venera" and "Soviet" between the years 1960 and 1990), but I have my own research project I should be working on so I didn't read all of them. If I can help anymore, let me know!

I've been digging through New York Times archives here. I haven't found much, but I did find one more opinion based article entitled "Report From Venus" dated January 28, 1971. Granted, it's on page 34, so it may not be the best, but it still appeared. In it, the author (unknown) suggests that the US needs to rethink how it's running the Apollo program, as it did have it's two successes at that point with the the be at manned moon missions, but the Soviet expansion to exploring other planets and eventually collected samples seemed increasingly like a more viable measure than manned missions. In the last paragraph though, he notes that cooperation between the two programs seems to be more likely, with there being a lack of resources in both programs.

Edit: In another article from January 27, 1971, author Walter Sullivan wrote "Report Accepted Here." Sullivan expressed some skepticism about whether or not Venera 7 actaully landed on Venus. While not stated in the article, this may have something to do with some of the previous Venera 4 mission not being as successful as the Soviets initially claimed. He eventually accepts it as truth, though, as the data from the Venera 7 was more consistent with a landing craft and, as he believed, the Soviet's had nothing to gain from lying about the success of landing, again going back to the Venera 4 mission.

It's not much, but I do hope it helps some. I plan on digging a bit more through there to see if there is anymore out there on this.