The only exchanges that matter are GDAX, Bitfinex, Gemini and Bitstamp. All foreign trading volumes do contribute somewhat, but they mainly affect their own market. I remember when South Korean exchanges were trading $5000 above western exchanges, which is beyond insane, but the western markets didn't give one single damn. Later on South Korean premiums vanished and became just a few hundred instead of thousands -- this perfectly indicates that continents have different demand standards and don't necessarily steer the other side up or down with it. That's the benefit of having different exchanges all operating different order books.