There is a fine but clear distinction between what the New Testament refers to as the "world" in some places, such as John 3:16 ("For God so loved the World... etc."), and in others, such as John 15:19, 1John 2:15-17 and James 4:4.
The first refers to humanity at large, and we are told that God loves it.
The second refers to what some people like to call "the System," the establishment, or - some movie freaks like myself - as "the Matrix," and we are told not to love it, or else we may become God's enemy!
What most Christians seem to refer to as "the World" in that second sense, is non-believers.
A favorite group to be included in that category these days are Muslims, for example. Strangely enough, not the Jews, even if for the sole reason that their Holy Book makes up the first two thirds of the Christian Bible.
Some atheists are also included in that group of the common Christian concept of "the World," (if a believer is willing to admit that Jesus, James and John must have referred so any sort of people at all in those above mentioned Scriptures), although - in the case of Christians in the U.S. this doesn't apply to American atheists.
Jews and Americans enjoy a special status and are somehow exempt from the mystery group of people that might possibly constitute "the World" that Jesus and His disciples admonished us to stay away from.
However, taking a closer look at Jesus' life and the Early Church history, we may discover quite a different picture than that common concept of "them Hottentots down yonder" as referring to "the world."
If we take that dusty Bible off the shelf and actually start reading the Gospels instead of settling for that weekly sermon with a few Bible verses tossed in, we begin to see that the sort of people Jesus was actually having the most trouble with were not the Romans (pagans and foreigners), but the religious community of His own people!
He said to His disciples, "He that receives you, receives Me, and he that receives Me receives Him that sent Me."
In other words, those He referred to in John 15:19 must have included or consisted of those who received Him not.
Was Jesus in fact referring to the religious establishment - among others? Folks living in our own country, that we adore every night on TV? Could it be possible that they might be part of "the world" that His true disciples are not supposed to be part of?
After all, it's hardly a temptation to fall head over heels for the hottentots we have nothing in common with.
It must have been tough for Jesus and His disciples to be rejected by the very ones they were supposed to have the most in common with (same God, same religion, same background and culture, and yet worlds apart).
It was still tough for them half a century later when Christians were banned from any synagogue in the world.
And that was before Paul got soft and gave it one last shot at converting his own "chosen" people, & went back to Jerusalem against the explicit warning from the Lord that this was going to be his death, and it was, eventually.
So, perhaps Jesus wasn't talking about the hottentots and pagans, after all, when He was talking about "the World." (But maybe they're included in "the World" that God loves, in John 3:16, and we're supposed to love them likewise?)...
"The World" that neither Jesus nor His true followers have never been a part of is the large majority of those who will simply always, throughout history refuse to receive those whom He has truly sent.
It may be hard to recognize His true disciples sometimes, because they may have broken some of the establishment's rules, similar to the way Jesus and His original disciples did in disrespecting the Sabbath and associating with prostitutes and other outcasts.
They will even make mistakes and commit sins, the way God's people have throughout history, since claims of "infallibility" are reserved for the untouchables and merchants of forgiveness of the established false religionists, and the world will come out to point their fingers at them, only to find themselves poking their finger right in God's eye, and hear Him repeat, "He that is without sin among you, let him cast the first stone!"
Maybe what Jesus referred to as "the World" isn't defined as much by anyone's "religion," as one's reception of His true emissaries and ambassadors.
As far as I can see, the established religious System still rejects, refuses and even persecutes the true disciples of Christ just as they have always done.
I guess it's something difficult to relate to unless one has made that type of experience himself.