I will not do anything past 2020 for the history sections unless they were born after 2020, as many events are too recent. Website still incomplete.
Personifications that have animals on their flag (or seal or symbol, if they lack a flag) will have the features of that animal. Once they gain a trait, they will not lose it, even if the symbol, flag, or seal that gave them that trait is gone, although sometimes, if they gain a new animal on their flag after having a different animal, the traits of the new animal can supersede the older traits. If a country has never had any sort of symbol/seal/flag with an animal on it, they will never have animal traits.
Additionally, personifications will also gain some of the instincts of the animal(s) they have traits from. They have to be careful about this; if they neglect or attempt to push aside that part of themselves, their animal brain can overwhelm them and leave them in an almost feral state. However, some personifications use this to their benefit as a way to dissociate from the real world and their problems and take a break.
When they switch into human form, their outer animal traits are hidden away. However, their internal organs and traits will remain the same, even in human form. The human form just makes them look human, so it is only a cosmetic change. Additionally, being in human form with animal traits can often become distressing for them. They cannot stay in human form for too long, as the places where they are meant to have traits (i.e. if they have wings but are in human form, their middle back) will become itchy as their body tries to revert back to its normal state.
Personifications with animal traits can also imitate the noises their animals make, especially those with the traits of mammalian creatures.
However, they often struggle due to the fact that they live in a human-centric medical world and are assumed to have the same biology as regular humans and countryhumans without animal traits, despite the fact that this is wholly untrue. Much discovery of the true complexity of the internal organs and biology of animal-traited countries has come about in the modern era with the invention of things like x-rays, as there have been no opportunities to dissect countryhumans, and their biology varies from countryhuman to countryhuman. Before these inventions, anything strange about the biology of a countryhuman with animal traits was chalked up to "magic."
Eagles and lions are some of the most common animals to see as a country's animal traits due to their popularity as symbols for nations.
Personifications with reptilian traits often get cold very fast (unless they are mythological creatures) and could be argued to be somewhat cold-blooded.
Due to their size, personifications with wings often have to get a running start or jump off of something high in order to take off. Once they are in the sky, their flight is fine.
The gland that secretes the oils used to help preen the wings is located in the elbow of the wing and not the tail feathers, allowing those with wings to preen even if they don't have tail feathers.
Claws are connected to the finger/toe bones of the countryhuman, and therefore, they cannot be cut very much without causing bleeding.
When countryhumans gain teeth-related traits—i.e., fangs or elk ivories—they do not gain them immediately as they would with other traits, but rather lose their teeth as one would lose their baby teeth and regrow the new teeth. This means these features will often show themselves later and can sometimes take years to come into effect, as losing all of their teeth and regrowing a set of fangs would take about five years. If they are only losing one or two teeth, they'll probably have it finished in under a year.
Countries with the traits of Western dragons who can breathe fire have an additional organ for that purpose. The organ repurposes part of what it eats as fuel (i.e., oils from the food and things like that), which allows it to store the fuel for its fire. Because of this, their fire is limited and affected by their diet. They can "run out" of fire and need to wait to build back up their fuel storage. If their diet is something that is inefficient as fuel, that will also affect how much they need to eat before they have a good buildup of fuel.
Mythical animals, such as phoenixes, will often grant the countryhuman with their trait abilities that are more magical in nature than based on biology, as the animal is magical, and not a real creature.
Diagram of an Avian Countryhuman Respiratory System (Drawn by LostIslands)
Personifications with bird or dragon traits have six "lungs," as they have the breathing system of a bird (explained here and here). It is all still located where the lungs would be in a normal human body, but they would have the two air sacs from a bird's respiratory system, as well as normal lungs, which are smaller in overall size, allowing the organs to take up roughly the same space as normal lungs.