Almost one-third of Americans believe the US will be invaded by a foreign power within the next decade.
When asked if 15 "dangerous political scenarios" were likely in the next ten years, 31% said yes.
The United States has been the dominant power in the postwar era and maintains the world's most advanced military force.
In 2021, American defence spending will be $801 billion, nearly three times that of China's $293 billion.
Half of those polled by YouGov thought the United States was at least somewhat likely to lose its status as a superpower.
The survey, conducted online between September 1 and 4, was conducted by YouGov and published on September 7.
Overall, Republican voters were more pessimistic about America's future in the coming decade than Democrats.