Many (pro?)fessionals, suppliers and manufacturers often talk about ANSI flanges, ANSI fittings etc. Just do a search on any Standards providers website for ANSI B16.5, ANSI B16.9, ANSI B16.10 etc.
You will not find that standards, because they do not exist.
Many years ago there was, as an example, a ANSI B16.5 standard. In 1988 it became ANSI/ASME B16.5 and in 1996 it became ASME B16.5. However, there are still many suppliers and manufacturers that refer to ANSI or ANSI/ASME and that's nots correct. There are also other standards which have changed to ASME and are still being miss-quoted in documents. Below you will find some examples, of the history, of particular ASME standards.
If you've read any of the articles above you will understand that ANSI and ASME work together, but that many standards have been adopted by ASME and are appointed since a long time, as ASME standard.