The reason for that is because getPreviousValue stores the cookie value at the domain level and because you are going from pitneybowes.com to pitneybowes.us you lose that value because you can't read cookies across domains. It looks like you are using s_gpv_pn as your cookie name to store that value.
Browsers these days are very restrictive on exchanging data across domains because of security reasons, so its going to be hard to accomplish such a feat. A scenario you could try is use a query string parameter on all url's that lead to .us!
A better question is why are you doing this - maybe I can help solve the ultimate goal differently?