Looking at the index used for it, it has 34 different indicators. USA is first in 18 of these and top 10 in another 8 (they are by the way ranked 175 in healthcare acces). That's also on prevention, detection, response, norms and risk.
I'm not the right one to consider whether the indicators are good or bad or if the US was in fact the potentially best prepared or these, but I can see that some of the strengths are thrown away by Trump and Kushner (or was based on facts that didn't really stand the test). I'm very well aware of the major lacks in the US health care and have seen the numbers of beds and ICU beds plenty of times (one of the few things things I could easily be sceptical about is that it doesn't seem like ICU beds are taken into account (only beds in general are))
Personally I would be careful about making any conclusions about whether it's a good ranking or anything. It is pretty thorough afterall, but that doesn't necessarily mean that they haven't focused on some of the wrong things.