That's not entirely true, there are may reasons; my friend has a startup in TJ working with professional cross-border migrants because of the immense pain it is to migrate to the US, mainly costs associated with living expenses but also the delays in approval. Hell, even getting his wife approved to come to the US, as a Mexican national married to a US citizen with a dual national child cannot enterthe US aas freely as you are making it out to be.
I think this is the whole victim becomes the perpetuator thing that is all too common in the Human Condition.
They welcomed Ukrainians fleeing the war with open arms, I helped feed and help them find legal resources to get processed in the onset of the war in '22 into San Diego, but when it's 'lesser then' like Russians/Belorussians or other Latin Americans, SEA or Arab nationals fleeing war, famine, or climate change the prejudices were obvious.