How do we know that Christ died for all believers?

Christ's death is representative of God's redemptive plan for humanity, specifically for believers from all backgrounds, as indicated in John 3:16. The context of this verse underlines that while God's love is broad, it becomes effective through belief. The metaphor drawn from the Old Testament story of Moses and the serpent illustrates that faith must be rooted in God's provision for salvation; just as in that story, salvation through Christ is made effective for those who believe. Thus, Christ's death is indeed a universal offer, but its efficacy is contingent upon individual faith in Him.