In an interview with Kerrang!, Campbell describes the experience fondly, stating that, "it got me thinking about how we were in a country with no particular reason for being there, and how immediately welcomed we felt when those kids helped us out and put us up for the night".

[4] This idea that individuals can find like-minded people thousands of miles from home stuck with Campbell, and the monuments near the Santiago bus station signified this connection, hence the name Sister Cities.

They sent postcards to fans with a minimal version of the album's cover art on one side and a short excerpt from the title track, "Sister Cities", on the other.

Once the password was deciphered and entered, the site revealed a teaser video for the album with clips from various songs and reflections from the band's members on the making of the Sister Cities.

[17] Timothy Monger of AllMusic saw Sister Cities as a natural successor to No Closer to Heaven, making "a move away from the spry pop-punk of [the band's] early days to create something heavier and ultimately darker".

praised the "deft manoeuvring and brute force" that the Wonder Years employed to enact a genre change, saying that Sister Cities "preserves the band's distinct stylistic markers and singer Dan Campbell's emotive power while applying it all with greater maturity and deliberation".

[18] Mischa Pearlman of Under the Radar similarly declared Sister Cities "a phenomenal album that not only transcends genres but which also only feels like the next phase of a career already 13 years short that has a long and exciting future ahead".

[24] Sister Cities was seen by some as an altogether departure from pop punk, with Thomas Forrester of GIGsoup saying that the Wonder Years had "definitely climbed beyond the constraints of the genre".

[23] Dave Beech from The Line of Best Fit similarly declared the track "a takes-no-prisoners opener that rolls in a pounding drumbeat before exploding in to the sort of blistering catharsis of later Movielife material".