How well do you think Biden did compared to Clinton, Obama 2012, Obama 2008 in the Chicago, IL area (McHenry, Lake, Kane, DuPage, Kendall, Will, Cook) counties? Do you think he underperformed? In these counties the results are as follows:
Biden 66.7%
Trump 31.3%
Clinton 65.1%
Trump 28.8%
Obama 64.5%
Romney 33.9%
Obama 68.1%
McCain 30.7%
Like in most Big Metro Areas, Hillary had a massive swing with white voters (plus what she gained with Latinos canceled her loses with Black voters). Naturally, Biden's smaller improvments with whites (Already voting quite high so not lot of room for growth) were wiped out by Trump's Latino and Black swing. (And Latinos here didn't even had those enormous R+20 swings that Texas/Florida saw)
Just look at these congressional districts in Cook County that are mostly white (Compared to this one in LA):
2012 | 2016 | 2020
IL-05 +34 +47 +46
IL-09 +32 +45 +44
2012 | 2016 | 2020
CA-30 +33 +43 +39 (*This one has a big latino minority so the gains didn't hold)
Now look at the mostly Latino/Black ones:
2012 | 2016 | 2020
IL-01 (Black) +59 +54 +49
IL-04 (Latino) +64 +69 +63
So yeah, it seems Hillary's overperformance and Biden's underperfomance in Chicago was nothing out or the ordinary given the national trends.