In Chicago, Starbucks has concentrated many facilities on a small territory, perhaps to gain a competitive advantage there. We see that the facilities are spread interestingly too: moving away from the core to the north-west, the inter-between distances gradually increase. Other vector directions remain mostly unexplored.
In Seattle, the company seems to have used a mixed strategy—both high concetration at a key area and high spread across the region. If we consider city populations, the Seattle branch serves ≈7170people/facility, while the New York branch serves ≈44500 people/facility. This means that it may still make sense to seek expansion in New York.
We can see that the locations of the facilities in New York are evenly distributed, covering a large territory, which allows the company to reach as many people as possible. To achieve such an even and strategic distribution, we may assume that a data science team is working behind this. At the center-top we can notice a "two-by-two" pattern.
If we look at the locations of the cities with the most Starbucks-owned facilities in USA, we may see a certain concentration on the East and West coasts. Note that the threshold for a city to be shown on this map is 22 facilities—other cities may still have a smaller number of existing facilities. You can click on this map to see it enlarged.
It is likely that the investments made in the different facilities vary a lot as well, which these maps can't capture well. Choosing the best locations alone is not sufficient to develop a good strategy.