According to Exodus 20:2-3
"I am the Lord, your God, Who took you out of the land of Egypt, out of the house of bondage. You shall not have the gods of others in My presence.
There are various other instances where "your God" is said in reference to the Jewish nation.
Are there any sources that show Hashem being called the God of any other nation or people?
'Behold, I am the LORD, the God of all flesh; is there any thing too hard for Me?
Yes, there is such a passage:
Hosea 2:23 ...I will have compassion on her on whom compassion was not had, and I will say to a people that was not my people: Thou art my people, and they: Thou art my God.
Israel cannot be "her on whom compassion was not had," since God called Abraham from idolatry to be sons of the living God and showered them with mercy above any nation; and from the rest of Scripture we know who "My People" refers to, namely, "Israel:"
2 Samuel 7:10 And I will appoint a place for my people Israel, and will plant them, and they shall dwell therein, and shall not be disturbed any more, neither shall the children of iniquity afflict them any more, as they did before.
So we see that God explicitly says that another people shall Israel shall be called His people, and that, therefore, they will say of Him, "Thou art my God."
But this isn't so shocking or sandalous, since converts to Judaism from other nations were existent, very much so, and therefore considered as much a part of Israel as anyone else: there was a very real conception of non-Jews by birth being capable of becoming Jews by circumcision, that is, of converts to the Jewish faith.
Judith 14:6 Then Achior seeing the power that the God of Israel had wrought, leaving the religion of the gentiles, he believed God, and circumcised the flesh of his foreskin, and was joined to the people of Israel, with all the succession of his kindred until this present day.
And of course there was the belief among the Maccabees that uncircumcised state of even uncircumcised Jewish children was 'heathenish,' and needed corrected as part of the crusade for restoring the tradition and orthodoxy to the Hellenized Jews:
1 Maccabees 2:46 And they circumcised all the children whom they found in the confines of Israel that were uncircumcised: and they did valiantly.
Moreover, God selected the Israelite people to be a light to the Gentiles, that is, the leaders and showers of the way, not the sole beneficiaries of the way:
Isaiah 49:6 And he said: It is a small thing that thou shouldst be my servant to raise up the tribes of Jacob, and to convert the dregs of Israel. Behold, I have given thee to be the light of the Gentiles, that thou mayst be my salvation even to the farthest part of the earth.
God chose Israel, but His sights were to all mankind, with Israel at the helm, showing the way, exemplifying the grace God grants to sinners, and showing the excellence of keeping His law, and the fruits thereof. The salvation and mercy He had on Israel was intended for all men, but He needed to form a people who were fully His first, in order to show that this is possible, admirable, and that in the very act of choosing a people among infinitudes of people, that it was all by the mercy of God: since He didn't choose Israel for its greatness: this is how the mercifulness of God is shown in choosing a special people to be a light to the Gentiles.
The haftarah for P' Ki Tisa (excerpted from I Kings 18) concludes (Nusach Ashkenaz) with the the verse
וַיַּרְא֙ כָּל־הָעָ֔ם וַֽיִּפְּל֖וּ עַל־פְּנֵיהֶ֑ם וַיֹּ֣אמְר֔וּ ה֙ ה֣וּא הָאֱלֹהִ֔ים ה֖ ה֥וּא הָאֱלֹהִֽים׃
And the people saw and fell on their faces and said: Hashem, He is G-d, Hashem, He is G-d.
They don't say ה׳ הוא ﭏקינו (Hashem, he is our G-d) and they only come to the realisation after turning aside to follow false deities (Baal being the one in question in this episode).
Throughout the prophets, we find references to G-d's universality, perhaps most famously in Zechariah (14:9)
וְהָיָ֧ה ה֛ לְמֶ֖לֶךְ עַל־כׇּל־הָאָ֑רֶץ בַּיּ֣וֹם הַה֗וּא יִהְיֶ֧ה ה֛ אֶחָ֖ד וּשְׁמ֥וֹ אֶחָֽד׃
And Hashem shall be King over all the earth; In that day Hashem shall be One, and His name one.
In Reb Avigdor Miller On Tefilla (great book) one of the kavaonos he says for 'elokainu' in shema is that right now he is our G-d, but in the future he will be recognized as everyone's G-d. So while Hashem is the G-d of the whole world and the creator of the whole world, it isn't widely recognized.
הֲל֣וֹא כִבְנֵי֩ כֻשִׁיִּ֨ים אַתֶּ֥ם לִ֛י בְּנֵ֥י יִשְׂרָאֵ֖ל נְאֻם־יְהֹוָ֑ה הֲל֣וֹא אֶת־יִשְׂרָאֵ֗ל הֶעֱלֵ֙יתִי֙ מֵאֶ֣רֶץ מִצְרַ֔יִם וּפְלִשְׁתִּיִּ֥ים מִכַּפְתּ֖וֹר וַאֲרָ֥ם מִקִּֽיר׃
To Me, O Israelites, you are just like the Cushites —declares the Lord. True, I brought Israel up from the land of Egypt, but also the Philistines from Caphtor and the Arameans from Kir.
No. G-d is not just the G-d of the Jews but the G-d of all people. Moses said:
"If this G-d is G-d, he would live on every mountain. In every valley. He would not be only the G-d of Israel alone but of all men. It is said he created all men in his image. He would dwell in every heart. In every mind. In every soul."
