Gallup Poll: Greatest enemy of US: China 20% Iran 16% North Korea 16%
Russia 9% Iraq 7% Afghanistan 5% Syria 3%
February 20, 2014
http://www.gallup.com/poll/167501/far-fewer-americans-say-iran-no-enemy.aspx?

Who is the greatest enemy of the United States? (open question)
China 20% Iran 16% North Korea 16% Russia 9% Iraq 7% Afghanistan 5% Syria
3%

Gallup poll based on telephone interviews conducted Feb. 6-9, 2014, with a
random sample of 1,023 adults, aged 18 and older, living in all 50 U.S.
states and the District of Columbia.
For results based on the total sample of national adults, the margin of
sampling error is ±4 percentage points at the 95% confidence level.

Interviews are conducted with respondents on landline telephones and
cellular phones, with interviews conducted in Spanish for respondents who
are primarily Spanish-speaking. Each sample of national adults includes a
minimum quota of 50% cellphone respondents and 50% landline respondents,
with additional minimum quotas by time zone within region. Landline and
cellular telephone numbers are selected using random-digit-dial methods.
Landline respondents are chosen at random within each household on the basis
of which member had the most recent birthday.

Samples are weighted to correct for unequal selection probability,
nonresponse, and double coverage of landline and cell users in the two
sampling frames. They are also weighted to match the national demographics
of gender, age, race, Hispanic ethnicity, education, region, population
density, and phone status (cellphone only/landline only/both, and cellphone
mostly). Demographic weighting targets are based on the most recent Current
Population Survey figures for the aged 18 and older U.S. population. Phone
status targets are based on the most recent National Health Interview
Survey. Population density targets are based on the most recent U.S. census.
All reported margins of sampling error include the computed design effects
for weighting.