To anyone outside the USA, this is old hat. Yes, latency matters for interactive traffic. Yes, the Atlantic (and Pacific) oceans are big and light ain't getting any faster.
Ah, well it could be. Light travels something like 66% of the speed in Fiber as compared to air. There have been attempts to design things like a balloon network across the Atlantic by HFT folk. It'll happen eventually.
RTT based on the speed of light should be 54 ms. Say 70 ms because it won't go as the crow flies, so could actually get twice as fast in theory.
You're discounting TCP ACK overhead, and time taken by switches.
Ping doesn't use TCP and the time taken by switches can be reduced, theoretically.