You're exactly right. Religion was used as a foil against Communism in the Cold War. It was the Good Christian USA vs the Evil Atheist USSR.
"In God We Trust" was adopted as the official motto of the USA in 1956. "under God" was added to the Pledge of Allegiance in 1954.
Regarding putting "In God We Trust" on currency, Representative Charles E Bennett said "In these days when imperialistic and materialistic communism seeks to attack and destroy freedom, we should continually look for ways to strengthen the foundations of our freedom" [1].
"In god we trust" was a swipe against the UK monarchy. The US government rejects rule "By the Grace of God". In most western monarchies God anoints kings and queens. But God has no role in picking the president. The root of power in the US is "the people". Those people trust that God could step in if needed, but they don't expect God to play the active role he does in monarchy.
Given that historical context, it is funny to see the phrase now used to support religion.
"In God We Trust" was adopted as the official motto of the USA in 1956. "under God" was added to the Pledge of Allegiance in 1954.
Regarding putting "In God We Trust" on currency, Representative Charles E Bennett said "In these days when imperialistic and materialistic communism seeks to attack and destroy freedom, we should continually look for ways to strengthen the foundations of our freedom" [1].
[1] http://history.house.gov/Historical-Highlights/1951-2000/The...