I'm assuming PR is working more O/D from the USA, specifically the WC, due to the population of the Filipino community, I highly doubt they are trying to get connecting traffic from AS outstations. I think Chicago and Las Vegas are the two most populated communities not on a seaboard, and considering the biggest ones are LA/SF/Hawaii, I don't see this being particularly useful by partnering with AS. Unless they really want to become a gateway for Asia, but that is speculative with the amount of airlines in Asia that offer more as is.
Oh and they already fly to Las Vegas.