Why do you think that locking children up in cages is not popular with Americans? You don't know that but you're making assumptions that could be based on human decency.
Why would that be unpopular with Americans when at least the Trump supporters believe that the immigrants are to blame for their poverty?
From:
https://www.vox.com/policy-and-politics/2018/6/18/17475740/family-separation-poll-polling-border-trump-children-immigrant-families-parentsTwo new polls find that the US government policy of separating children from their parents at the Mexican border is very unpopular with the general public... Sixty-six percent of voters...told Quinnipiac they opposed the policy...A poll conducted by Ipsos exclusively for the Daily Beast found similar results....Fifty-five percent of respondents stated they disagreed...while 27 percent agreed.
Now, admittedly there was more support for the policy among republicans, but the number who identify themselves as republican has been dropping steadily over the years. The public by and large rejects the family separation policy.
Why would that be unpopular with Americans when at least the Trump supporters believe that the immigrants are to blame for their poverty?
Many (perhaps even most) Trump supporters may favor locking children in cages, but again they don't make up a majority of voters in the country. (And even some Trump supporters think it goes too far... in one of the polls it wasn't even a majority of republicans who supported it.)