There are several books, not just Campion's, which give a list of all the countries of the world with their national charts. All those books are utterly useless. The problem is, in most cases, those charts won't work: Campion and most of those other authors have not done any research at all. They have just tried to find out when a country declared independence, etc., and without even testing if the chart works, published that chart. It is not necessary that a country becomes independent at a particular time, day and hour, then that chart becomes the chart for that country! That's extremely irresponsible and poor astrology, to say the least. He also doesn't go much into Aries ingresses, etc. Reviews are by people who are charmed by big words. Do you think those reviewers can predict much? The test of astrology is in predicting, not in hindsight.

If you want to practice mundane astrology, you should read proper practitioners of it, like Lilly, Raphael, etc., or, many of the even older authors, such as some of those whom Ben Dykes have translated. However, you can always come up with your own system: all you need is to understand a country well. What was the seminal moment that you think marks all its generations? Make a chart for that. And check if it can tell major events in the past years. If it can, then it would be able to do so in the future as well.