Substituting text but only if it is not part of another word

For example, I have an address in one cell and I want to get rid of the state. The state is not always in the same place so I was using =SUBSTITUTE and omitting the last bit which lets you choose which occurrence of the text you want to substitute, but my problem is that if the state appears as part of another word it does this:

Original text = 123 SUNNY BUNNY LANE, NEW YORK, NY 123456 USA
Substitute = 123 SUN BUN LANE, NEW YORK, 123456 USA

How can I replace occurrences of "NY" only if it is on its own and not part of another word within the string?

Thanks,

Soph

Not really because the addresses are not consistently structured (eg. in China the address needs to be sort of backwards so the state comes first).

If only we lived in a world where everything was always consistent, I would be a very happy bunny indeed