The 1st amendment covers "US persons." A US Person is a term of art broader than a citizen. OTOH since this is for a visa review that a non citizen wouldn't need I don't see where it comes into play.
Read textually, it covers “the people...of the United States" [1][2].
The courts have interpreted this to mean people physically within the United States, with some ambiguity at the borders.
[1] https://constitution.congress.gov/constitution/preamble/
[2] https://constitution.congress.gov/constitution/amendment-1/
Also, going through social account history is not only for reasons of oppressing freedom of speech. Presumably you might want to reject visa applications from someone who threatens others with murder
That's how the law works in the US, due to the textualist nature of our jurisprudence.
Sort of [1]. (“We the people” has specific case law.)
[1] https://constitution.congress.gov/browse/essay/pre-3/ALDE_00...