Dawg2019
You asked about American calibers and guns that will take Cape Buffalo and the answer is yes!
I personally do not care what rifle or caliber others use and see no benefit to being critical of any of them.
Nor do I see any benefit to denying proven facts and claiming that a .45-70 can not kill a cape buffalo; it has been done and is being done with increasing frequency.
Obviously, the .460 Weatherby is an American caliber that can take buff too, but I do not shoot one.
My Big bore arsenal has all killed cape buff and a many other interesting animals:
1. Model 1895 Winchester in .405 WCF has killed Cape Buff, water buffs, Nilgai, and other exotics
2. Model 1886 Winchester .45-70 has take several Cape Buff, many bear, many hogs, many plains game
3. Model 1886 Winchester .45-90 has taken elephant, several Cape buff, leopard, plains game, bison, etc
Non of these rifles wears a scope either.
There is abundant proof that these rifles with the right bullets can take dangerous game. People that deny this are either ignorant of the facts or just touting their favorite rifle, a common practice that can be done without criticizing other rifles or cartridges.
I am not recommending any rifle or cartridge to you, just answering your question. Please have fun selecting the rifle that best suits you and your intended use.
Good hunting.