Illegal border hoppers from south of the border that have been apprehended have included many of Middle Eastern origin.
Your argument is invalid.
In 2001, we KNEW about some Yemenis who tried to get across, and we even knew that they were offering $30K a head and could not get in.
OTOH, the one example we have of a border hopper who was apprehended IN the USA before he could do a terrorist act was from [ahem] Canada.