Imagine that Texas left the Union. They might renounce the debt, they would also forfeit Social Security, military pensions, Medicare for old people, etc. Maybe most people would be ok with this, but I suspect (for example) a lot of retired military guys would not be happy with it. Texas could of course choose to replace their mission pensions with State of Texas pensions, but the question would be "where does that end".
So, it's not so simple as you postulate.
If the only reason a state like Texas can justify staying in the Union is due to the debt, then that should tell you something....