MeanMrMustard the way I see it, Jeremiah chapter 25 is including Jerusalem (which was the capital city of Judah) and all the other cities of Judah in the list of that which the chapter calls the "nations" who shall serve the King of Babylon seventy years (Jeremiah 25:11, 17-18, 25 [ASV]).
While the list of nations probably doesn't mean that calamity will come to them in that specific order, to me it clearly states (even if what is states is incorrect) that the calamity comes first to Jerusalem (begins at Jerusalem). I don't see the distinction you and some others make between the use of the word "beginning" (or "begin") and the word "starting" or "first" at Jeremiah 25:29. In your quotes of Jeremiah 25:29 you left out the words which said specifically where the calamity was said to begin, namely the city of Jerusalem. For example, note that Jeremiah 25:29 (ASV) says "For lo, I begin to work evil at the city which is called by my name ...." Verses 18 - 26 lists those who receive calamity and verse 17 (ASV) calls all of those groups "nations", and verse 18 includes Jerusalem in that category of "nations". Please keep in mind that in BCE times many cities were "nation states" (modern scholars of the history of the ancient Middle East call them such) and thus were nations (such as a the cities which the OT book of Joshua says the Jews conquered in the land of Canaan). Jeremiah 25:17 -18 (ASV) says "... and made all the nations to drink, unto whom Jehovah had sent me: to wit, Jerusalem, and the cities of Judah, and the kings thereof, and the princes thereof, to make them a desolation, an astonishment, a hissing, and a curse, as it is this day". Since verses 17 - 18 (ASV) indicates that Jerusalem is called one of the "nations" then when verse 11 (ASV) mentions that the "nations shall serve the king of Babylon for seventy years", it is including Jerusalem as one those nations - even if in fact Jerusalem did not serve the king of Babylon for literally seventy years (and even if in fact the prophecy in the name of Yahweh partially failed).
The conservative Christian evangelical commentary called The International Bible Commentary: With the New International Version (a revised edition of 1986; the former edition used the RSV scripture text), which has F. F. Bruce as its General Editor, says the following on page 780 about Jeremiah 25:15-29 [the use of italics in the quote is that of the commentary]. "... The scope of the Lord's fury embraces all nations beginning with Jerusalem and Judea and then 'the uttermost parts of the earth' (18-26; 28: 33). ... After Judah the list groups places affected by direct Babylonian campaigns (e.g. Egypt in 601 B.C. and Dedan, Tena and Buz in Central Arabia--all mentioned in contemporary inscriptions). ... 20-26. all the kings of ... : this repeated phrase has caused some commentators to reject these verses as late, but such phrases occur in contemporary historical texts. ..."
The conservative Christian evangelical commentary called The New Bible Commentary Revised (Third Edition, copyright 1970), edited by Guthrie and Motyer, says the following on page 642 about Jeremiah 25:11, 15, 29 [the use of italics in the quote is that of the commentary]. "11 The duration of exile, seventy years, ensures that all the original exiles would be dead before its end; this is a round figure approximately correct. ... 15 Cup of wine is the symbol of Yahweh's inescapable wrath over Judah and other nations (cf. Ps. 75:8; Is. 51:17). Babylon is His agent. ... 29 Observe that the fury of the Lord begins with Jerusalem (cf. v.18) and extends to other nations who also deserve the divine chastisement." Notice it says "Judah and other nations" and "Jerusalem ... and ... other nations", thus by its use of the word "other" it is treating Judah and Jerusalem each as a nation also. That backs up what I said above.
Regarding the phrase "as it is this day" at Jeremiah 25:18 it might just mean the time period in which Jeremiah wrote his account (or whoever wrote the account), namely the time of the exile of the Jews. Or, the phrase might be an insertion into the account by an editor.