PRS is a private military and weapons research organization and contractor funded largely by the US government. They date back to at least WWII. They are responsible for the creation of Bloodshot, the HARD Corps and the child-soldier group of Psiots known as Generation Zero, among others. Think super-powered Haliburtan.
Harada Global Conglomerates is the combined properties, businesses, etc of Toyo Harada, the world's most powerful Psiot. He has been manipulating governments and economies since WWII in order to build a corporate empire and shape society to his vision for it. Harbinger Foundation is the Psiot recruitment and training division of the HGC, where Harada finds, activates and trains his private Psiot army.
MERO is the US government organization responsible for researching and defending against extraterrestrial threats. Currently, XO Manowar works for MERO in return for the protection of his people.