With so many people crying for unity of the nation, why does it seem so many are disingenuous about it?

With so many people crying for unity of the nation, why does it seem so many are disingenuous about it?
Campaigns come and gone, activist, pundits, and more, people always talk about the nation coming together and working as one for the betterment of the country. Yet no matter what it seems to always end up as ”us” vs ”them”, and even one group seemed to have something that benefits the nation the group that isn’t them will oppose it, degrade it, try to sabotage it, anything but support it. If each group, party, etc. will only support their group or party line no matter what, where and how is this unity ever to manifest itself?