The last year was a difficult year for the Ultimate Universe. Reed Richards and his Children of Tomorrow turned Europe into a citadel called the City. The Asian countries reformed themselves into the South East Asian Republic, a heaven where mutants are in charge.
On the home front, a successful attack on the White House and the capital building destroyed the seat of power in the United States. The highest ranking surviving cabinet member, Secretary of Energy Howard, was sworn in as president. Carol Danvers, former director of S.H.I.E.L.D., was appointed Secretary of State.
Faith in the Government is at an all time low, causing several states to rebel and Texas to secede from the union. In the west, militia groups run the day, actively killing anyone looking for safe passage through that part of the country. In the East, everyone is trying to get by as best they can despite the chaos, but it is obvious the country does not have a direction anymore.
Thanks to the current chaos in the country, Captain America has the future of the Ultimate Universe on his shoulders. While capable shoulders, it is still unknown what actions he will take. Will he do what is required of him, or will he do what is necessary for a lasting peace?
What is required in this situation is to protect the government from all threats internal and external. Steve Rogers can do that with little problem. It would simply be a matter of taking all the resources the Government has and using them to his advantage. He could use all sorts of goodies that the government does not want civilians to know about.
He can also call in some major favors from all superheroes in the East coast, and send them all over the country in strategic strike teams. See how long Texas lasts as an independent country when Hulk and She-Hulk rip apart its infrastructure. How long can those militia groups in the Southwest continue when Giant Men wander through there? This is in addition to the more reasonable villains in lockup, all of the uncategorized mutants, and heroes in hiding. If they all mobilized under Captain America, they would be unstoppable.
However, that might not be what is necessary for lasting peace. Captain America will need to restore faith in the American way of life. He will need to address the many problems the United States has done to mutants and to super humans in the last 10 years. There are many things he can do, but in the Ultimate Universe, they will not be easy decisions. No matter what happens, someone will lose.
Of course, when Captain America takes the burden for you, it means you do not have to accept responsibility.