Different affiliate/tracking links vs. Universal book link

I was just reviewing Thomas’ podcast episode, How to Spend LESS Time Marketing Your Book - Author Media. In it, he recommends using different Amazon affiliate links for all your different marketing avenues (website, social media, blog, emails, etc.) to track where the most sales are coming in from.

This makes sense, but I am confused on one thing—Thomas has also said to make sure to use a universal book link, so that international readers can easily buy your book. I use Books2Read, generating one singular universal link, to which my Amazon affiliate code is attached.

How can we use different tracking links if we’re also using a universal book link?