All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
This slogan: Allaah, the nation and the king, is considered a minor Shirk [associating partners to Allaah] with regard to its wording, as by saying so, one parallels the nation and the king with Allaah. This is like the saying of some people: Allaah, the nation and the revolution. As regards its meaning and reality, then the matter might even be more serious, since they considered the Status of Allaah like the status of the nation, revolution and the king. Indeed these three terms, the nation, the revolution and the king, have become nowadays like idols which are worshipped beside Allaah. People declare their allegiance or enmity based on these matters, and this is also used to disunite the Muslims. In addition to this, many revolutions and kingdoms were founded on secular principles which contradict Islamic jurisprudence.
To conclude, it is not permissible to pronounce these terms, and they are considered among the minor Shirk, and they might even be a major Shirk [associating partners to Allaah, thus becoming out of the fold of Islam].
Allaah Knows best.