Living outside of Israel is considered idolatry

 Drashos Haran (04) That sin which is cause for apprehension on the Blessed One's part as potentially resulting in the destruction of the Jews is idol worship, to which the sin of the golden calf was similar in character. For the other transgressions do not arouse the Blessed One's wrath to such a great extent; idol worship is to be much more feared in this regard. And there is more reason for apprehension of this sin in the desert than in the land of Israel. For the Jews knew that the other lands were under the ordinance of stars and constellations, as our sages state (Kethuboth 110b): "All who live in the land of Israel, it is as if they have a G-d; all who live outside the land of Israel, it is as if they do not have a G-d." This is because the other, gentile lands are under the ordinance of heavenly plenipotentiaries, an ordinance which cannot be changed except through miraculous, Heavenly intervention (this being the intent of "for he will not forgive your sins"). Therefore, if one lives outside the land of Israel, because he is under the ordinance of a star or of a constellation, his prayer is not so readily accepted as it would be if he lived in the land of Israel, which is not under the dominion of a chief, an officer, or a ruler, but of the Blessed One Himself,

Kesubos (110b) One should always live in the Land of Israel, even in a town most of whose inhabitants are idolaters, but let no one live outside the Land, even in a town most of whose inhabitants are Israelites; for whoever lives in the Land of Israel may be considered to have a God, but whoever lives outside the Land may be regarded as one who has no Godץ Has he, then, who does not live in the Land, no God?56 But [this is what the text intended] to tell you, that whoever lives outside the Land may be regarded as one who worships idols.

Rambam (Melachim 5:12) At all times, a person should dwell in Eretz Yisrael even in a city whose population is primarily gentile, rather than dwell in the Diaspora, even in a city whose population is primarily Jewish. This applies because whoever leaves Eretz Yisrael for the Diaspora is considered as if he worships idols as I Samuel 26:19 states 'They have driven me out today from dwelling in the heritage of God, saying 'Go, serve other gods.

Ramban (Bereishis 24:03) THE G-D OF THE HEAVEN, AND THE G-D OF THE LAND. The Holy One, blessed be He, is called the G-d of the Land of Israel, as it is written, They know not the manner of the G-d of the land. and it is further written, And they spoke of the G-d of Jerusalem, as of the gods of the people of the earth. So also the Rabbis have said:. “He who lives outside the land of Israel is as if he had no G-d, as it said, For they have driven me out this day that I should not cleave unto the inheritance of the Eternal, saying, Go, serve other gods