So, I'm not entirely sure how it came about now, but I somehow stumbled upon some of the awesome, historically-based, and actually serious fanfiction written for the very not-serious anime "Hetalia: Axis Powers".
So, here are some of my favorites. There will be more to come.
Wendigo by AnAppleofDiscord
Series: Hetalia - Axis Powers
Rating: PG-13
Warnings: Profanity, violence and please read all of the author's stated warnings.
Location: Fanfiction.net
Status: Complete - 26 Chapters
Summary: Arthur was so used to foes attacking him as a nation he forgot his vulnerabilities as a man. A longtime enemy settles the score; Alfred gets caught in the crossfire.
Comments: Probably the single best chaptered fanfic I've read in over a year. Of course, it was practically tailor-made for me - supernatural elements, adventure, and a truckload of dysfunctional-yet-loving family feels. The dialogue is brilliant. The interaction between the Kirkland brothers is pure gold. And, the author has a talent for making readers love the characters even when they're being unlovable. When they're caustic, bullheaded, and chronically prone to saying the wrong thing at exactly the wrong time. Of course, when the lead father and son finally do voice how much they really care for one another, it's all the more earned for the misunderstandings and headbutting along the way. Also, Arthur's "I will call you 'boy' until..." speech is possibly the greatest dad speech ever.
Home of My Smile by Kelbora
Series: Hetalia - Axis Powers
Rating: PG
Warnings: Mentions of violence.
Location: Archive of Our Own
Status: Complete - Oneshot
Summary: For once the imperial conquest didn't matter - snubbing France and winning the race for treasure and territory didn't matter. Just holding the boy and marveling at the feeling that mutual completion brought was the only thing in the world.
Comments: Because, yes, while I love the historical fiction as you'll see in my below recommendations, it's father!England/Arthur and son!America/Alfred that really got me into reading Hetalia fanfic. Because I'm a sucker for family feels. And, this is a very sweet entry there, being set in the 1600's before the revolution that would divide father and son.
Good Afternoon, Mister Adams by Gemini Star01
Series: Hetalia - Axis Powers
Rating: PG-13
Warnings: Some profanity.
Location: Fanfiction.net
Status: Complete - 6 Chapters
Summary: Alfred Jones observes and interacts with his founding fathers in the weeks leading up to the inevitable drafting of the Declaration of Independence. (Also based on the musical 1776.)
Comments: My favorite parts of this one are the moments where people catch glimpses of Alfred's true nature as something more than human, as the literal embodiment of everything they're striving for. The way the author describes it and builds to John Adams' revelation near the finale is beautiful.
Rabble in Arms by ProcrastinatingPalindrome
Series: Hetalia - Axis Powers
Rating: PG
Warnings: Mild profanity and some brief innuendo.
Location: Fanfiction.net
Status: Complete - Oneshot
Summary: America has doubts about his newly won independence, and requires a little fatherly reassurance from his founding fathers.
Comments: Despite being from a different author, this oddly and wonderfully reads like a direct follow-up to the above "Good Afternoon, Mister Adams".
Naturally One by General Kitty Girl
Series: Hetalia - Axis Powers
Rating: PG
Warnings: Mild profanity.
Location: Fanfiction.net
Status: Complete - Oneshot
Summary: March 1873, a grand gala is held to renew U.S./Canadian relations after the conclusions of the Alabama Claims and Fenian Raids. However, this is also Matthew's first chance to see his brother since the conclusion of the American Civil War.
Comments: Just a dash of history this time but plenty of brotherly bonding. Plus one poor chef nearly killed by Alfred's attempts at French.