So yes, it imposed abortion on half the country. I'll also point out it imposed, through the trimester framework, when life begins (ie. when a baby is viable to survive outside of the womb and thus have an interest in life).
The imposition of the idea of when life begins on the entire country is exactly what you just argued against.
So in this case, Roe imposed not just abortion on the states that didn't want it, it also imposed an idea of when life actually began.
Or do you not know what imposed means?