The Queen's Rise to the Top - Chapter 20: Sue You for libel

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

Ten years ago, mana descended upon Earth in the form of Gates that opened into other worlds. These Gates contained Magical Beasts of unfathomable strength and power that preyed upon humans and sought the destruction of everything around them.But along with the Gates, humans gained the power of Gifts—super abilities that allowed them to fight back against the monsters and take back their world.Now, the Superhumans with Gifts are tasked with defending the people and ensuring that the Gates, which open all over the world, do not bring about the end of them all....Jason Marc was just your regular seventeen-year-old high school student whose father abandoned him ten years ago. He worked two part-time jobs while also helping his mom with her diner to aid with the finances, but he could have never guessed that his entire world would change on the eve of his eighteenth birthday.Now, with more power than any one man should possess and an army at his beck and call, Jason works toward protecting those close to him while finding out the truth behind the emergence of the Gates—and preventing the end of the world.

“Ding! Soulbinding has been successfully completed; you will now head to the Heaven Awaken World.” After hearing this, Zhao Fu’s vision darkened as he fell to the ground.

With bleak prospects in the real world, Zhao Fu’s life is turned around when countless crystals fell from the sky one night, which people could use to enter an alternate, game-like world. After obtaining an ancient Chinese empire’s legacy, Zhao Fu uses his intellect and resourcefulness to develop his own empire from a tiny village. However, with enemies both in the real world and in the Heaven Awaken World, he must make brilliant decisions and use creative schemes to survive.

- Description from Novelupdates

In the early world of immortal cultivation, there was no physical cultivation among immortal cultivators. And a top bodybuilder who came from the earth has opened up a new path here and became the ancestor of physical training.

- Description from novelbuddy