Rose Egypt, I believe that unless you're applying to PhDs with an MA, conference participation isn't necessarily an expectation, even if you are applying with an MA, I don't think it'll hurt applicants if they haven't had anything accepted just yet. It can't hurt to show that you're serious about your work with this kind of experience, but I wouldn't worry about the relative prestige of conferences at this point. However, to answer your question, a professional or graduate conference at an accredited university (with full departmental support: tenured faculty involved, if not running it / participating) is the basic standard. From there, prestige increases based on whether it is graduate or professional, the host institution, the reputations of the presenters / panelists, whether it is institution-bound as opposed to regional, and better yet, national, or international in scope. See comparisons:
Nice to have: paper in your field of interest presented at an interdepartmental / interdisciplinary graduate conference held by a department at your own institution
Very nice to have: paper in your field of interest presented at a graduate conference at a top-ranked R1 which is not your home institution, and that also has a specialist / dedicated department in your field of interest
Highly impressive (as a PhD applicant with BA or MA): paper in your field of interest presented at a regional or national professional conference: e.g. NEMLA, MLA, etc.
I think we need to be careful with presenting at "societal" conferences, e.g. "The (insert author name here) Society," etc. Some are really well renowned, attached to amazing institutions and run by reputable scholars, but others are tin-pot, and there's not much use in using up a great paper where it won't get you noticed (unless you desperately want the practice).
As for the international thing, well, I'm an international who is in her second grad program in the U.S., and I think it's probably true that if anything, adcoms would like to see a name they recognise. I don't, however, think the location is a real problem provided the conference falls roughly into one of the criteria above. If the conferences are undergrad conferences, they're also indications of your seriousness and commitment, but are obviously regarded less highly in terms of academic rigour.