There is still residual thou weakening anticatholicism in the USA. Would they care?
They would. The US would never nuke Rome, considering...
1.) There is a neutral country in Rome, the Vatican. If you nuke Rome, you would probably kill the Pope, or take out a lot of Catholic leadership. Any proposal to nuke Rome would probably get vetoed by France as well.
2.) America, particularly the Northeast, has very, very high Catholic populations. Catholicism is the largest Christian sect in the United States. It would mean political suicide for the President, and probably a lot of civil unrest in heavily Catholic regions of the country.
3.) Rome as a city has much more historic value than the other targets. Rome was essentially the center of Western Civilization for many centuries, even a millennia. It would be more logical to nuke Genoa, Trent, Trieste, or Torino than Rome.
4.) Whomever is President just alienated just about every Italian-American for nuking Italy's capitol, every Irish-American, Italian-American, French-American, Polish-American, or any Catholic in the country, or around probably 30%-40% of the United State's population.