> the best network I’ve ever benchmarked was AWS and measured about 55µs for a round trip

What is "a network" here?

Few infrastructures are optimised for latency, most are geared toward providing high throughput instead.

In fact, apart from HFT, I don't think most businesses are all that latency sensitive. Most infrastructure providers will give you SLAs of high single or low double digits microseconds from Mahwa/Carteret to NY4, but these are private/dedicated links. There's little point to optimising latency when your network ends up on internet where the smallest hops are milliseconds away.