In the USA, "pagan" usually means what scholars would call "neopaganism": modern religions which try to recapture the spirit of ancient European paganism (sometimes without knowing much about it), like Wicca and Druidry. Since all other pagans are polytheist and some Wiccans aren't even theist at all, they can be regarded as pagans by courtesy.
This is closest to how I use and see "Pagan(ism)" used in America; also to add with what
@Quintessence said, over-applying the term to everything not Christian makes it, more or less, useless.
When I converse with the Pagan Community at large, or when I go to the Pagan section of bookstores, the commonly encountered cultures are Norse, Greek/Roman, and Celtic. Slavic culture is sadly scarce (they took a bigger Christianization blow than others), but I see a lot of Slavic Pagans in Heathen circles - Heathenry referring thus to Norse, Slavic, and Uralic (Estonia and Finland) cultural beliefs. Egypt is also present in the bookstore sections, and I'll find Wiccans who use Egyptian deities, but actual Egyptian polytheists - Kemeticists and Asetians -
don't consider themselves to be Pagan. Some even resent that Wicca uses their gods.
Thus Wicca is... problematic for me. And for those who like to classify things for a sense of order. Many Wiccans that I have encountered tend to "borrow" from many cultures, namely that of Buddhism and Hinduism, as well as indigenous American beliefs - or what can be gathered of them. This leads to the notion that these things are a part of Paganism, yet in speaking with Hindus and indigenous American tribes, none of them have considered themselves "Pagans," don't recognize the term, or prefer not to associate with it in favor of their religious terms. Buddhism is the odd one out for this, as they've got the "everything" thing going, but for myself - and those I associate with regularly - they're an Eastern religion/philosophy, not a Pagan one.
In short, Paganism - forgetting what was with the word in it's origin - refers to modern reconstructive efforts and faith systems of pre-Christian European cultural beliefs.