That never happened. Muslim and Sikh Americans, and anybody who could mistakenly pass for them, north African or middle eastern, were treated as internal enemies by the government, its private contractors and by "fellow" american citizens. If you felt unity in that moment, then I surmise that islamaphobia didn't impact your friends and family. I did not experience a unified country after 9/11.
Instagram was the only "real" social media I was engaging with (besides LinkedIn, I guess?) specifically because of this. I could still keep up with (most) of my friends goings on but without my mother explaining how her racist ideas weren't actually racist in 5 paragraph essay form. I could see dank memes, and babies making cakes and generally have fun.
Then the world caught fire. The politics came from Instagram HARD. And the more time I spend on it (while myself feeling more politically engaged) the more I'm recognizing its shortcomings. It's not a placid information farm with a cute cat facade anymore. It's the same putrid swamp as everywhere else, but you have to have an image (or an image of text) associated with whatever you're trying to say.
TL;dr- Instagram users skew "younger", so I like it more than Twitter or Facebook. Other people seem to agree.
However, the normal venues for politics having been rendered unusable, it's now become totalising; all communications channels will tend towards politics all the time.
This will continue until either sanity is restored and the miscreants permanently removed from the political arena, which seems very unlikely; they win and get opposition effectively criminialised, which also seems unlikely (although this is what happened in Hong Kong); or some exogenous event happens like 9/11 and the country can unify against external enemies rather than internal ones.