"The Immigration Act of 1965... created preference categories for science, math and engineering-trained immigrants to come over. [Asian countries] were producing a surplus of college-educated adults but lacked a sufficiently developed domestic economy to adequately absorb them. The 1965 Immigration Act, in trying to bolster America's own domestic needs, inadvertently helped absorb that surplus [and] influenced the American perception that Asians were somehow naturally gifted in math and science because there was a disproportionate number of immigrants coming from Asia with those skills."
Later extended to cover all Asian immigrants.
There was certainly demand to emigrate to the US, but it was forbidden. This act alone I think goes a long, long way to explaining why Asian Americans are a fairly recent phenomenon and "weird" to American culture.
Just to let you know, you're not alone there as a country.
As I said, nebulous; I hadn't really pursued the line of thought very far, just tangentially as it came up elsewhere. I hadn't known about the 1965 Act, and its existence and the above analysis just instantly explained so much so well and without reference to Asians somehow being magically different; just that the math/sci trait had been selected for within the Asian-American population.
Not that it rules out other explanations. But it's so blindingly obvious (in retrospect :) that the Act would have some effect along these lines, that Occam's Razor raises the bar for other explanations by a lot.
I know about the immigration act's effect on the Asian American population because I was an Asian/Asian American Studies major. That your comment received so many upvotes explains some of why these beliefs are so pervasive.
Moreover, our curricula are incredibly tone deaf if this major shift in the American population isn't required knowledge for passing American history.