Are Japanese terms for the United States and the Soviet Union likely to be confused by native speakers of Japanese?

Question

In the comments section of Do the Japanese believe that USSR dropped nuclear bombs on Hiroshima and Nagasaki?, it's speculated that Japanese people agreed with a statement that the Soviet Union carried out the bombing of Hiroshima and Nagasaki, because the respondents were thinking of the United States, but were confused by the similarity between "USA" and "USSR".

Assuming that the survey was made in Japanese, is it plausible that "USA" and "USSR" was used, and that a large number of native speakers would confuse which country "USA" and "USSR" refer to? Alternatively, are there other terms for the Soviet Union which could be mistaken for the United States?

Answer 1

That's not likely to happen, as long as the survey was conducted in Japanese.

• USA → アメリカ, 米国{べいこく}
  _{As like most nations outside US do, we prefer to abbreviate the country's name to toponym.}
• USSR → ソ連{れん} (ソビエト)
• Russia → ロシア
• ("united states" → 合衆国{がっしゅうこく})

If someone should believe that the Soviet Union was America, then it's another failure of public education, but irrelevant to linguistic matters.

PS
I Googled for Japanese source of "25 per cent of young Japanese people believe that the bombings were carried out by the USSR" but I could find nothing.