The US abandoned the gold standard in two steps. First in 1933 when FDR ended Americans' right to exchange paper dollars for gold. Then in 1971 President Richard Nixon "closed the gold window" and denied foreign governments the ability to exchange the US dollar for gold.
From the Stephen Moore and John Tamny in the American Spectator:
With the real economy weakening due to rising inflation, Nixon’s approval ratings tanked, which allowed the relatively minor scandal of Watergate to force his resignation. Some years after he left office, Nixon told a group of friends and advisors that the policy decision he regretted most was taking America off the gold standard, and that had he not done that, he could have withstood the Watergate scandal.
Further reading: Nixon Shock




