Also a couple of things to note:

1. Submarine cables can't go in a straight line, since they've got to, you know, go down to the bottom of the ocean. (Which, you may have heard, is quite deep.) Also, a cable with a length of several thousand miles tends to have some slack.

2. Your packets may take a very curvy route from one city to another, even when they're not geographically that distant. This may be because your ISP is bad (and has poor/limited routes), geographic or geopolitical concerns, or just because of the way the Internet infrastructure is built. On the US's west coast, I often experience latencies 60%+ slower than the theoretical minimum when accessing servers in the central or eastern US. (e.g. SF -> Des Moines, IA at 70ms).