RL wrote:
In the US, he would not be eligible to run for president as any candidate must be born in the country. This was put into the Constitution back in 1787 because of fears that a foreign born person, particularly British, could swoop in and take over the country. It's probably an outdated concept now since we're very much a nation of immigrants, but it would be very hard to pass an amendment.
RL, I assume the "he" to whom you refer would be Clark (Superman), and in that case you would be correct, except the Vice President must meet the same qualifications for office. (Interestingly enough, that is not explicitly stated in the body of the Constitution, but has been ruled so by the courts, since the Veep could become First at any time).
As to the immigrant portion of your comment, that is also right on the money. (My maternal grandmother passed through Ellis Island from Italy way back when.) But you might not be aware that, in the southwestern portion of the country, someone who advocated an amendment which denied citizenship to babies born in the US whose mother was an illegal would receive a great deal of support.
Such a campaign would polarize the country, of course, but such is politics.