The US in general is hurt in the luxury segment by the big chains (MR/HH/Hyatt) seeming not to have the same standards as their international properties, but there are still many world-class luxury properties throughout the US. I mention NYC specifically because I've found even the luxury offerings from the smaller chains / boutiques to be mediocre. Also, even properties that are well-regarded on FT also seem wildly inconsistent.

It'll be interesting to see how the Aman does.