This is very ingenious, but it really is without merit unless you can show me somewhere else in Scripture where the Jews are referred to as 'The Nations.' If you can't, I'm afraid you are guilty of shoe-horning the text to fit your theory.
'The Nations' appears quite a few times in Scripture but always (as far as I can see) referring to the Gentile nations that surround Israel. Exodus 34:24; Deuteronomy 4:27; Revelation 20:8.
Bearing in mind that the same Hebrew word goyim is used for nations & Gentiles, we can start with the promises to Abram:
Gen. 22:18 And in thy seed shall all the nations of the earth be blessed; because thou hast obeyed my voice.
Zec. 2:11 And many nations H1471 shall be joined to the LORD in that day, and shall be my people: and I will dwell in the midst of thee, and thou shalt know that the LORD of hosts hath sent me unto thee.
Isa. 11:12 And he shall set up an ensign for the nations, H1471 and shall assemble the outcasts of Israel, and gather together the dispersed of Judah from the four corners of the earth.
Isa. 49:6 And he said, It is a light thing that thou shouldest be my servant to raise up the tribes of Jacob, and to restore the preserved of Israel: I will also give thee for a light to the Gentiles, H1471 that thou mayest be my salvation unto the end of the earth.
Zec. 2:11 And many nations H1471 shall be joined to the LORD in that day, and shall be my people: and I will dwell in the midst of thee, and thou shalt know that the LORD of hosts hath sent me unto thee.
Isa. 11:12 And he shall set up an ensign for the nations, H1471 and shall assemble the outcasts of Israel, and gather together the dispersed of Judah from the four corners of the earth.
Isa. 49:6 And he said, It is a light thing that thou shouldest be my servant to raise up the tribes of Jacob, and to restore the preserved of Israel: I will also give thee for a light to the Gentiles, H1471 that thou mayest be my salvation unto the end of the earth.
Your statement is strictly correct, in that plural the nations (goyim) refers to the gentile nations. (goyim goyim), whereas the singular refers to Israel or a specific nation. [Please don't correct my Hebrew tenses - I'm using Strong for the word search but do not know Hebrew.]
For this study, notice Zec. 2:
11 And many nations H1471 shall be joined to the LORD in that day, and shall be my people: and I will dwell in the midst of thee, and thou shalt know that the LORD of hosts hath sent me unto thee.
In God's sight the believing nations become my people though I do not think whole nations are referred to, but believers out of the nations. And of course, we will not be attacking Jerusalem - heavenly or earthly, spiritual or carnal. As God's people, citizens of heavenly Jerusalem, we suffer attacks from the nations,