There was some vocal support for him before the War but most Italian-Americans patriotically supported the war effort. But in any event, they would all want to see Italy retain its Brenner Pass border--why, they would ask, should the now-democratic Italy have to pay the price for the sins of the Fascists? (After all, there had been plenty of support for the Nazis among Austrians, including those who lived south of the Brenner Pass...) Indeed, even as it was, the Italy-US peace treaty ran into some trouble in the Senate because of italian-Americans who thought it was too harsh on Italy.
"Opposition to the Italian treaty was headed by the Committee for a Just Peace with Italy, Inc., of which Charles Poletti, former Governor of New York, was chairman. Other members included Roger N. Baldwin, former Representative Clare Boothe Luce, Col. Robert P. Marshall, former high-ranking official of the American Military Government in Italy, John O. Pastore, Governor of Rhode Island, Judge Ferdinand Pecora, and many members of university faculties and the press. The committee, basing its campaign on an analysis of the treaty made by former Assistant Secretary of State Adolf A. Berle, Jr., inserted full-page advertisements in newspapers all over the country, declared that: it does not make sense to turn Italy over to communism by withdrawing troops while we are bolstering up Greece and Turkey against Russia; that America will pay Italy's reparations; and that Italy deserves better at our hands than this treaty because of the part that her partisans and troops played in hastening Allied victory. The committee asked Congress to declare officially the end of the war with Italy and pass such other necessary legislation as was done in the case of Germany after World War I.
"Taking a similar stand were the Sons of Italy in America, American Chamber of Commerce for Trade with Italy, American-Italian Congress, several Italian-American labor organizations and the American Committee for Religious Freedom in Italy and Evangelical Committee for Relief in Italy. The two latter groups were represented at the hearings by Dorothy Thompson and Vincent Sheean, also members of the Committee for a Just Peace with Italy."
In the end, the treaty was ratified 79-10, the arguments of Seantors Vandenberg and Barkley prevailing:
"Vandenberg read into the Record in his opening speech a letter from a representative of an Italian news service recently arrived in New York, who said that “almost all Italians who have our country's destiny at heart… and the overwhelming majority of the members of our government and of the Constituent Assembly” feel that “we cannot possibly wait any longer for a starting point on which to build up our national economy… If we had bread and jobs for everyone in Italy, I too would fall in with the Italian-Americans in urging that ratification be at least postponed. But unfortunately we cannot afford to wait… unquestionably the morale of the Italian people could be improved by the ending of the state of war and by the withdrawal of occupation troops.” Senator Barkley, who had been in Italy in April, reported that “although the Italian people would have preferred a more favorable treaty, they prefer this treaty to chaos and no treaty at all.”"
But if there was that much opposition to the treaty as it stood, one could imagine the reaction to a treaty that deprived Italy of part of South Tyrol.