That is not really the issue. Of course those who are saved in this Age are members of the Church.
What is in view is whether or not the Twelve Tribes are still in existence. That is the debate I have been part of, anyway,
When Apostle Peter quotes from an OT Scripture that was originally given to the children of Israel, and then Peter applies that to Christ's Church; that's not an issue?? IT MOST DEFINITELY IS! It proves how Apostle Peter saw Christ's Church in relation to God's Israel.
I have already given my view on this, in that we do not become children of Abraham but sons of God. That is the distinction between the Church and all those of faith under Old Testament Economies.
Then you deny what Apostle Paul taught in Galatians 3 about those of Faith are the children of Abraham:
Gal 3:7
7 Know ye therefore that they which are of faith, the same are the children of Abraham.
KJV
(Have I really... come to a true Christian forum here? Many times it doesn't seem Christian at all, with all the folks here that are bent on denying so much of the written Word of God!)
You don't know what Faith Abraham's Faith represents, do you? which is why Apostle Paul said those of Faith are the children of Abraham. It's because the blessing God gave to Abraham INCLUDED The Gospel of Jesus Christ. Abraham's Faith was in the same Gospel Promise we have believed, that's why he is our spiritual father per Paul.
You're latter tirade only contained a few points of validity, the rest was pure doctrinal traditions from men.
Because the Church foundation of Eph.2 includes God's OT prophets has nothing to do with stupid exalting. It has everything to do with The Gospel of Jesus Christ, for The Gospel is found in the OT Books also, even starting at Gen.3. The Book of Isaiah is one the greatest OT Books about God's Salvation through His Son. THAT... is why those prophets are included in the foundation of Ephesians 2, along with the Apostles and our Lord Jesus as the Cornerstone.
But the corruptions of men's traditions you've latched onto try to destroy that connection of the OT prophets linked with the foundation of Christ's Church, and that includes their importance still TODAY for Christ's Church, even all the way into God's Eternity since God gave them to write about it in His Word!
You're parallel to America is outlandish also. I'm sorry that my ancestors of the American Revolution whipped Britain's butt, twice, but that was history, get over it.
With your attempt to use Ezra as evidence for your view, you have turned God's Holy Writ upside down, just in order to keep your tradition of men. No wonder your tradition denies the scattering of the ten-tribed house of Israel by the kings of Assyria PRIOR to Judah's later Babylon captivity!
By not recognizing the majority of Israelites were not there in the return per the Books of Ezra and Nehemiah, you have just left the small remnant of the house of Judah that returned from Babylon as the ONLY seed of Israel.
2 Kings 17:18
18 Therefore the LORD was very angry with Israel, and removed them out of His sight: there was none left but the tribe of Judah only.
KJV
See, you can't make Scripture like Ezra 2:70 mean all Israel without turning other parts of God's Word upside down. You wouldn't have done that if you actually knew your OT history better. Go back to 1 Kings 11 and read forward to that 2 Kings 17 chapter.
Note this also:
2 Chron 11:13-17
13 And the priests and the Levites that were in all Israel resorted to him out of all their coasts.
14 For the Levites left their suburbs and their possession, and came to Judah and Jerusalem: for Jeroboam and his sons had cast them off from executing the priest's office unto the LORD:
15 And he ordained him priests for the high places, and for the devils, and for the calves which he had made.
16 And after them out of all the tribes of Israel such as set their hearts to seek the LORD God of Israel came to Jerusalem, to sacrifice unto the LORD God of their fathers.
17 So they strengthened the kingdom of Judah, and made Rehoboam the son of Solomon strong, three years: for three years they walked in the way of David and Solomon.
KJV
Starting at 1 Kings 12, old Israel was split into two separate kingdoms. Some of the people out of all the tribes of Israel in the north refused king Jeroboam's golden calf worship, so they went down to Jerusalem and sided with the tribes of Judah and Benjamin. The Levites in the north did also. Those in the southern kingdom were called "kingdom of Judah" (thus above), and also "house of Judah".
My point? ONLY those of the "house of Judah" went into the Babylon captivity by Nebuchadnezzar. The ten tribed northern "kingdom of Israel" or "house of Israel", was already... gone... out of the land by then.
SO HOW ARE YOU GOING TO HAVE TEN TRIBES RETURNING WITH EZRA BACK TO JERUSALEM AFTER THE 70 YEARS BABYLON CAPTIVITY WHEN THE TEN TRIBES WERE NOT... EVEN A PART OF THE BABYLON CAPTIVITY IN THE FIRST PLACE?!?
No, instead, you've just accepted a false history about the Book of Ezra of those who deny the real history outlined in God's Holy Writ. It shows you have not really looked into that Biblical history for yourself, but just took other's word for it.
In Luke 2, you'll find one Anna, who was of the tribe of Asher, and she spoke of Jesus. Does that prove all 12 tribes of Israel were back together in that day? Of course not, because OT histories reveals the ten tribes were scattered.
So when James 1:1 addressed the 12 tribes "scattered abroad", that's exactly... what he meant.
It means Israelites of the SEED of Israel scattered among the nations of Gentiles, not the other way around which is a stupid idea.