Interesting that the 2 US cities that stand out for not having a grid have very different histories that lead them to that.
Boston is one of the oldest cities in the US and has a very confusing layout because the roads were constructed gradually without central planning and many of the city neighborhoods were small towns that eventually grew together. In this way it has some similarities with the European cities on the right, although it’s obviously not nearly as old.
Charlotte on the other hand has only developed into a major city relatively recently and was developed at a time when suburban-style sub-developments were common.
You can really see the difference in a map of both cities. Charlotte has a neat grid downtown and it’s only outside the central part of the city that the streets start meandering. Boston, however, has an incredibly confusing downtown, while some of the outer neighborhoods have grids (although they are all different grids).