People forget that the point of the speech is right in the title. It's not about the health of the country or political ideals.
Once a year, the President delivers a speech on the stste of the union. It's about how divided the country is and whether or not that division is a threat to the nation.
If the country went full-fascist without a struggle that wouldn't threaten the Union. If the Republicans were voted out of existence and we became a socialist utopia that wouldn't threaten the union.
What is happening now, with one party increasingly refusing to work with the other side and intentionally breaking the systems that make government work? Yeah - that's a threat to the Union.