I think, all pretty recently (atleast in the 'States), there's been much news and noise about the abuse and fraud of these systems designed to help the downtrodden.
Now whether that's all true, has always been true, is propaganda...whatever, but it's easy for me to understand why sentiment has been changing as the spotlight is focused more and more on the abuse of the systems as opposed to the benefits.
I also think there's some 'hierarchy of needs' going on here, where as the economy shifts and more and more Americans are struggling to afford housing, groceries, and other necessities, it's easy to feel like you should be putting yourself first over strangers. Combine that with the prior point, and you have a great recipe to build resentment. Selfish, maybe, but I can understand how you get there.
This is NOT to say 'There is no xenophobia' or anything...racism in general is alive and well in the USA... but I have pretty sound-minded people around me starting to echo this mindset, and this is my best understanding of what's been brewing.
For what it's worth, the most effective propaganda is that which reinforces latent biases.
Humans en masse are selfish, self-serving, and tribal, so it's incredibly easy to believe that there is massive abuse of social services like SNAP/EBT, those delivering services are incompetent, and that we should investment more in fraud reduction.
However, the reality is that the US spends $3.75 for each $1 of fraud discovered. And, "fraud" includes clerical errors made by the government, so the actual ROI of enforcement is even lower.
So much of the propaganda -- "immigrants steal benefits paid for by hardworking US taxpayers, so we should ramp up enforcement spending to make more room for [white] citizens" is designed to simply reinforce our biases because it's just so darned believable to a cynical and tribal people.
In reality, spending more on benefits enforcement just loses taxpayers more money while cutting more US citizens off from benefits they both need and are eligible for. It results in the opposite of its stated goal and this is well known to any policymaker.
So if saving taxpayer money, and punishing those guilty of fraud, isn't the actual objective of all this toxic propaganda, you have to ask yourself what is.