I do have my doubts regarding why the border was not closed, but blaming Jews for not closing US south borders it is the same as blaming Jews for Trudeau's decision to bring Palestinias to Canada. Obviously Jews would not like it. After all, we all saw how those who are already in Canada for years, supposedly domesticated ones behave...
I think the reason for both steps is bringing in the future electorate ( in both cases), in the US, there is an additional pragmaticall side. Cheap work power, which is a necessity for an economic growth
The devil is as usual in details.
When the numbers of "imported" voters is too big, they are changing the country before getting its values.