Short answer: replace
Long answer: As you comment, the
scrartcl class, as well as others of the KOMA-Script bundle (as
scrlttr2) were designed with European (German) conventions in mind (based in
script package that implemented the rules of Jan Tschichold in 1987 (“Ausgewählte Aufsätze über die Gestalt des Buches und der Typographie” (Selected Papers on book design and typography), 2nd printing, Birkhäuser Verlag, Basel.). Also the NTG classes (of
ntgclass package) are "European" versions of standard classes.
I don't known much about American typographic conventions, but as these classes were created as European versions of the standard classes (
letter) that consequently are not European. In good Cartesian logic, this does not imply that
article have a pure American design, but I think that we may mostly assume that ... At least the default paper size is the US
letterpaper (11 by 8.5 inches) and not the usual A4 paper (297 by 210 mm) in Europe (the default in
scrartcl class). And accordingly, the default font size is also smaller (10pt instead of 11pt).
In case of doubt, use a unquestionable (?) "American" class available in usual distribution, as those related by the American Mathematical Society (AMS), the American Psychological Association (APA), or the American Society of Agricultural Engineers (ASAE).
(Disclaimer: This does not ensure fitting American conventions, neither is maintained by American pepople, nor it is an official or good design, only that is related with style of publications of a scientific American association.)
If you prefer the
scrartcl class to maintain the font of titles or some other feature, it is better that you specify exactly what you want, as Marc van Dongen suggest, but setting the most evident differences (kind of paper, font size and margins) is very straightforward: