In 1948, I really doubt the government could very well "crack-down" on anything without obvious limitations to the bureaucrats getting reelected, although I don't know how the mod treats the US. If they are basically a Truman government that mopped up the Pacific with Japan, but didn't have the chance to dominate and annihilate Germany with an alliance with the USSR, then the government will not have a Democrat Great-Society deep state in the works, and the public will lean heavily conservative.
The main effort is coming with a reason why the US, that is the Anglo-Saxons and general public, would be averse to an alliance with Europe. Worb came up with some pretty wild scenarios, and that was me tagging his post
, but the world of a victorious Reich - minus Kaiser
- would be heavily nationalist, or conservative, or traditionalist. Thus, the diversity within the US could become agitation for repatriation of Africa, and events to form nations of American-sphere powers being formed in the African continent. Japanese could very well be repatriated wholly as one, and then there is Taiwan, the Phillipines, and SE Asia for America to sphere-around.
The greatest conflict between America and Germany would be reconciling their modern governments, both are fairly well centralized after the war. America would likely go into full-steam ahead with extreme liberalism, granting the Civil Rights acts and using the excuse of a totalitarian Europe to rapidly expand immigration from the rest of the nations of the world. This could happen right as 1960 comes along. Both countries would then face the succeeding competition of socialising their governments as rapidly as possible, a race to see which one's economic value collapses first(they never see it coming), leading to a preemption by the Soviet remnants to attack either. America could become rapidly overpopulated in its coastal cities by 1975 and its market crash would send its government into a death spiral. Across the Atlantic, Germany could face extreme terrorism from nationalists, or conservatives, or traditionalists attempting to break free of the socialised labor and education, and censorship...
That's a little bit for now. Buona Fortuna!