I think Abba was a bit later on the scene in North America. I remember my older sister being a big fan, but for me I think they were radio starts with catchy tunes, but I never bought any albums or singles.
But I did love disco, and I think the BeeGees reigned supreme for me at the time. I think I had a pretty eclectic rock/disco/pop favourites, with some folk/pop as well, such as Carly Simon, Simon and Garfunkel.
Rock was very popular at my school though, so I was introduced to rock albums from friends, like ACDC, LedZeplin, Boston, etc. I still enjoy a good blast of rock from the stereo once in a while!