Yes, violent religious conflicts, like Northern Ireland, can happen in the United States of America.
In the United States of America, there has only been one Catholic President, and many Protestants still hate Catholics.
Many Protestant Christians in the United States doubt that Catholics are loyal to Jesus Christ and the Holy Bible.
The majority of African-American Christians are Protestant Christians, and there is aggressive anti-Catholic attitude among many African-American communities across the United States of America.
Because many Catholics vote for gay marriage rights and abortion in politics, many Protestants are becoming more and more anti-Catholic in America.
Many Protestants are willing to resort to violence to protect their religion, and this is, in fact, a part of Protestant history for centuries, when deeply religious Protestants resorted to war and military warfare to protect Bible Christianity.
This includes many Protestant Christians in the FBI, CIA, Homeland Security, USMC, US Army, US Navy, US Air Force, and throughout every fabric of American life.
Catholic church leaders in 2016 America recognize that many of America’s Protestant Christians assume that all Catholics will go to Hell.
Protestant leaders who embrace Catholicism or Catholic leaders are ostracized from the Protestant Christian environments. In other words, the quickest way to lose legitimacy as a Protestant Christian leader is to embrace or hug Catholicism.
Listen to one of the most influential Protestant Christian leaders criticize Catholicism:
For most Protestant Christians, the very existence of the Pope and the Vatican is an abomination.
All Bible-believing Protestant Christians are agreed with Rev. MacArthur that Roman Catholics are all going to eternal damnation in Hell.
Many Protestant Christians do not believe that the Protestant Reformation that started in 1517 is over, yet:
This Protestant Christian perception dominates among Protestant Christians in the United States of America, United Kingdom, Australia, Canada, New Zealand, etc.
Protestant Christians in India and other parts of Asia (Korea, China, Taiwan, Singapore, Indonesia, etc.) all assume that 100% of Catholics are going to eternal damnation in Hell, because they are not truly born again.
In other words, the world’s 1,000,000,000 Protestant Christians all assume that Catholics are going to eternal damnation in Hell because they are not truly born again Christians.
Thus, Protestant Christians are all seeking to convert Roman Catholics to Christ.
The strongest Protestant Christian force in Latin America is Pentacostalism. Many Roman Catholics in Latin America are converting to Protestant Christianity through Pentacostalism.
And many Latinos/Hispanics in the United States are evangelical Christians, who converted from Catholicism.
Most Hispanic evangelical Christians may have political disagreements, but they are mostly agreed that all Roman Catholics are going to Hell.
Religious divide is far more immutable than political ones.
Thus, Saudi Arabia and Iran conflict can escalate and lead to a world war. That should not surprise anyone in the West, given the history of Western civilization.
Protestantism is continuing to exert its power in the western world in traditionally Catholic areas, and this is by intention and premeditated converstion/proselytism efforts, targeting Catholics and Catholic communities.
In a similar way, you have to assume that such things are happening in the Muslim world.