This is an important question, since too many take for granted that God’s Israel and Christ’s Church are somehow separate.
     Since Dr. Bullinger was mentioned in the last question, let’s cover another doctrine from his work How To Enjoy The Bible, about the difference between The Church and Israel.
     On pages 149-155 of that same work, Bullinger separated Christ’s believers into two subgroups, The Church as compared with Israel. He goes into an essay that Christ’s Body of members cannot be separated, with one group experiencing the tribulation, and another group of members being taken out. Yet, he does just that with contrasting Israel against Christ’s Body of The Church. He obviously didn’t understand how most of the ‘house of Israel’ migrated out from the Assyrian captivity to form the Western Christian Nations of today. Bullinger then goes on to do a type of ‘re-unite’ of The Church with Israel in Christ’s Kingdom later, under the Eternal Israel.² (see the Lost Tribes study to really understand all this).
     This doctrine of creating a separation between God’s True Israel vs. The Church, has caused many to believe they are apart, when it is the non-believing sons of Israel who have parted from True Spiritual Israel, i.e. God’s Israel, which is His Body, and not any particular geographical area. The Church, or Christ’s Body, represents those believers on Christ of both Jew and Gentile, per Romans 2. To receive Christ Jesus as Savior today, is to inherit the Salvation Promise God gave through Abraham, to Isaac, then to Jacob, who was named Israel by our Heavenly Father. All believers on Christ Jesus thus become children of Abraham through ‘faith’, from both Jew and Gentile, and become inheritors of that Salvation Promise in Christ Jesus (Gal.3; 4; Romans 9; Rom.4; Gen.12; 17).
     Moreover, that new Name God gave to Jacob, that Name ‘Israel‘, became the Name of The Salvation Promise through Christ Jesus as Savior. For that word ‘Israel‘, ‘Yisra’el’ in the Hebrew means “God prevails”, or “to prevail with God” (Strong’s nos. 8280; 410; 3478). That’s exactly what Jacob did; he ‘prevailed’ with God’s help (Gen.32). And that word ‘Israel’ represents the Salvation Promise, first given to Abraham by ‘faith’, believing on The Lord Jesus Christ as Savior (John 8:56). Thusly, True Israel IS The Body of Christ’s believers, of all nations, of all peoples. They cannot be separate, and are not.
     One view of the “secret rapture” doctrine by some, is that the endtime tribulation is upon ‘Israel’, but not ‘The Church’. Thus they believe, and teach, that Israel will be left behind, while The Church is raptured out. But in God’s Word, The Church (Body of Christ), is ‘Israel’. That word ‘church’ means ‘a congregation’, in the ‘gathering’ sense. The word ‘church’ (ekklesia in the Greek), merely means “a popular meeting, a religious assembly”. It’s just a word applied to the Body of Christ’s believers. But the word ‘Israel’ is applied to God’s Kingdom under Christ (Rev.21; 7; Hebrews 8; Gal.6:15-16; Rom.9:6-8; John 12:13; John 1:49; Luke 22:29-30; Luke 1:68; Matt.19:28).
     Many “secret rapture” folks truly think God’s ‘Israel’ of today, are all non-believing Jews. They haven’t understood who, or where, God’s True Israel is today. The Lost Tribes studies help reveal that wherever The Birthright blessings God gave to Abraham, then to Isaac, then to Jacob (named ‘Israel’), and then to Joseph, and finally to Joseph’s two sons of Ephraim and Manasseh, then that’s where God’s True Israel is today. What? Never heard that before? Then you haven’t been properly taught God’s Word, for It is all written.
     Those ignorant of God’s True Israel today, cause their deception to become greater, as they do not apply endtime prophecy upon today’s True Israel as Christ’s Body, but to non-believing Jews and the middleast nation ‘called’ Israel only. “Well, all that latter day stuff is meant to happen upon Jerusalem and Israel,” they might say. “Well, I’m not part of Israel; I’m part of The Church, so I’m not going to be here for Satan’s tribulation,” they would utter. The matter of importance from God’s Word is, that the Western Christian Nations of today are descended from the ‘house of Israel’, and are most definitely True Israel. The ‘house of Judah’ are mistook for being True Israel today, and most of those in the Holy Land nation called ‘Israel’ in name only, do not even accept Jesus of Nazareth as Christ Messiah, our Savior. They haven’t understood that ‘Israel’ is The NAME of The Salvation Promise of ‘faith’, which God gave through Abraham, and was fulfilled by Christ Jesus upon the cross. So to our Heavenly Father, ‘True Israel’ is where the majority are who accept His Promise of Salvation, being in Christ Jesus. So just ‘where’ would that majority be located today? Where are the “ten thousands” of Ephraim, and the “thousands” of Manasseh? (Deut.33:17).

Footnotes:

¹  How To Enjoy The Bible, by E. W. Bullinger. (Kregel Publications, Grand Rapids, MI.), Reprint of 1916 4th ed., 1990, pp. 190-191.

²  Ibid., pp. 149-155.