Edit: Also this is based on (pre-tax?) income before transfers such as subsidized food, housing and healthcare which distorts comparisons (i.e. in the US, unlike almost every rich countries, only the poor get free or subsidized healthcare).
The overall poverty rate given is approx 15%.
While not a relative poverty measure the regular Census methodology you refer to has all the other weaknesses I mentioned but the biggest is it is based on a rather arbitrary level established in the 1960s then updated based on broad inflation. Not clear how relevant these thresholds are today - may be worse or better.
BTW - Census also has a relative poverty measure, known as the "supplemental poverty measure".
