A better way to phrase this question would be 'What could happen to me if I was a communist American in the US in the 1950s?'

A few good examples of things that did happen were the Hollywood blackballing of former actors, producers, directors, and crew due to leftist or socialist sympathies. The example of Charlie Chaplin being denied a visa to the US and never starring in another major film produced in the US is a good example of this. Another example I recently learned about was that J Edgar Hoover had Americans like John Steinbeck audited every year by the IRS due to the authors political sympathies. Although there may be some other reasons I am not aware of as Hoover was most certainly a man with imagined enemies. Also the state department fired most if not all there Chinese speaking or those with china experience around this time due to their close proximity to communist party when the Chinese were an ally against the Japanese. The anecdotes go on and on but I think you can easily see the consequences were social ostracism, blackballing, and a proclivity for further actions to be taken for several decades after the red scare. Good book written before the red scare about labor relations pre McCarthy is 'In dubious battle" by Steinbeck. It at least captures a lot of what got young men in the depression interested in trade unionism and socialism.

Source for State department Henry Kissinger "Diplomacy" Source for the Hollywood stuff Joseph Trento 'the secret history of the CIA' (Note this is mentioned in several sources I own but this one is just easier to pull from)

Jessica Mitford wrote a second biography / political memoir called "A Fine Old Conflict" where she talks about her work in the political left in 1950s California. She had connections to the Communist Party, as did her husband. She worked in anti-racist work and in labor organization -- her husband ran a law firm that did progressive work and defended Communists.

She does detail some formal hearings and investigations she was involved in, but one of the things I found most interesting and creepy was her description of trying to find non-political work--secretarial, clerking, teaching, etc. through classified ads. She would very often get far along in the interview process and then suddenly be dropped without explanation. She would later find out that government officials had visited the employer and strongly, strongly recommended that the employer not hire her, because Jessica Mitford was a known commie. It seemed to be a combination of federal agents and state and local government workers who followed her and her husband, and basically conducted this sort of shadow harassment campaign; if I recall correctly they visited not only potential employers, but friends and neighbors of the couple.

This, of course, was aside from the open social opprobrium they attracted:

In any event the CRC membership was well aware that the organization, and many of us as individuals, were frequently and prominently labeled Communist in the press. Whenever the Oakland Tribune had occasion to mention Bob or Bert, no matter what the context, the words “lawyers who represent Communists” would appear after their names. After Bob and I were subpoenaed by HUAC in the early 50s, the words “identified Communist” always followed any reference to either of us in the Tribune, a policy of that newspaper that ended only after publication of the American Way of Death in 1963.