Every time there is an electoral race there it's a major head ache for the rest of the world just as much as for the Americans which kinda makes you think what the entire fuss is about and why they don't let both of them be president if they want it so much.
Has that issue ever been raised in America?
I would like to point out that the reason the Romans had two consuls was as a check on the power of the highest office attainable in the state. A consul had a lot of power, and in the early republic would be the leader of the army during his term. Since the position was so powerful, the romans figured that the best way to check the power of that individual was to have another individual with the same amount of power. It's a system that seemed to work fairly well for the most part, although if the consuls were at odds with each other, they could veto each other and the system would break down into gridlock.
The American system also has checks and balances built into the system by the Constitution. The US government can be broken down into 3 branches: the Executive (President and his cabinet), Legislative (Congress), and Judicial (the Courts). A generally good way to remember how their power breaks down is like this: the Legislative makes laws, the executive enforces those laws, and the Judicial declares whether or not either side is playing by the rules (generally in accordance with the Constitution). Over the past 100 years or so, the power in the relationship has generally shifted towards the Executive, with presidents like Roosevelt and Nixon (among others) generally pushing the boundaries of their power. But the same gridlock seen in the Roman system is present in the American system, especially when the President belongs to one party and Congress belongs to another. The President can veto Congress' laws, but Congress can override the President's veto.
So the US doesn't elect both candidates because they do not need the check on the Presidents power. That role is already fulfilled by the Congress and the Courts.
Like you noted, the consuls existed in pairs as a check on each other. Each consul had the power to veto the other. The semi-mythical history of the Roman Kingdom (and more specifically, the story of the tyrant king Tarquin the Proud) taught the Romans that unchecked power was very dangerous. The vetoes of the two consuls served as a natural check over one another, the idea is that one consul couldn't be too self-serving because the other consul would veto the. It turned out that this system still had its flaws because the interests of the two consuls often aligned pretty closely (most consuls were wealthy upper-class patricians). Further checks were created with the office of the Tribune of the Plebs, which also had veto power. This was designed to make sure that the consuls were also taking the plebeians into account and not just looking out for the (generally better-off) patricians.
In the United States, rather than having power checked between two (or three) executives, power is instead split between completely separate departments. James Madison writes about this a bit in the Federalist 47:
The accumulation of all powers, legislative, executive, and judiciary, in the same hands, whether of one, a few, or many, and whether hereditary, selfappointed, or elective, may justly be pronounced the very definition of tyranny.
To Madison, it's not sufficient to simply have an internal check on power, but to divide power completely. To justify this, he quotes the French philosopher Montesquieu:
The reasons on which Montesquieu grounds his maxim are a further demonstration of his meaning. "When the legislative and executive powers are united in the same person or body," says he, "there can be no liberty, because apprehensions may arise lest the same monarch or senate should enact tyrannical laws to execute them in a tyrannical manner."
Madison was very concerned of any body accumulating too much power. James Madison speaks at length about checks in the Federalist 51:
But the great security against a gradual concentration of the several powers in the same department, consists in giving to those who administer each department the necessary constitutional means and personal motives to resist encroachments of the others. The provision for defense must in this, as in all other cases, be made commensurate to the danger of attack. Ambition must be made to counteract ambition.
To Madison, the ultimate check against one branch encroaching onto another is self-interest and ambition. Madison wants every branch capable of "self-defense". Madison felt that there was an inherent "weakness of the executive" branch. A divided presidency would be even weaker, and a big problem because it wouldn't be able to defend itself from the ambitions of Congress. If you agree with Madison, a divided presidency would actually increase corruption as the checks and balances would not longer work as intended.
After writing that all out, I noticed I didn't really didn't answer "Has that issue ever been raised in America?"
Interestingly enough, this was close to the initial state of affairs under the US Constitution. Whomever was awarded the greatest number of electoral votes was elected president while the runner-up was elected vice president. This ended up causing issues almost right away, as in the election of 1796 John Adams (a Federalist) was elected president and the runner up, Thomas Jefferson (a Democratic-Republican) was elected vice-president. This was a problem because unsurprisingly they did not get along at all. In fact, during Adams's presidency, Thomas Jefferson hired a newspaper editor to run a smear campaign against Adams, despite that they were ostensibly on the same team.
This issue was finally addressed in the 12th Amendment which attempted to make sure the president and vice president were joined in one ticket, and that the presidency would not be too weak and divided to effectively check the other branches.