Peru's score tumbled to 3.61 from 6.33 in 2016, while the number of Colombians who said migrants living in their country was a good thing dropped to 29 percent from 61 percent.
The first Gallup Migrant Acceptance Index was conducted amid the backlash following the 2015 migrant crisis in Europe when more than a million people headed to the continent fleeing war and poverty in the Middle East and beyond.
EU countries have long been at loggerheads over how to handle the influx of migrants, many of whom arrive in Mediterranean countries after perilous boat journeys.
The bloc's executive will unveil a plan on Wednesday which would legally oblige all members to host their share of refugees — something rejected by Poland and Hungary among others.
The proposal has been brought forward because of a fire on the Greek island of Lesbos a fortnight ago which destroyed a migrant camp holding more than 12,000 people — four times the number it was supposed to.
Among European countries, only Sweden and Ireland made the Gallup top 10 of most-accepting countries.
Ray said some people would be surprised by the positive attitudes in the United States, where President Donald Trump has made curbing immigration a cornerstone of his policy.
"Despite the fact that immigration is such a hot topic in the US, Americans are mostly very accepting of migrants," she said.