See this - https://en.wikipedia.org/wiki/2010_United_States_federal_budget#/media/File:Fy2010_spending_by_category.jpg
Approx - SS - 20%, defense - 19%, Unemployment/welfare/other mandatory 16%, Medicare and Medicaid 21% - you’re at over 75% of federal spending there.
You don’t pull that rug out from under the economy without serious repercussions. And then, all those doctors, defense contractors, people who run businesses near Army bases, etc - all depend on that money. Plus, slum landlords and others living of the avails of welfare.
And, nobody explains how, if you cancelled medicare or welfare what the people would do? Riot and loot grocery stores? Die in droves? You already have socialized medicine in the USA, it’s just crappy and paid for by the people with actual (often also crappy) health care. If a person who cannot pay shows up at a hospital, they still have to give them basic treatment. Who pays for that? It gets added to everyone else’s bill. Cut off medicare, and all those people will show up to get treated for free, and you will pay for them with higher premiums, and $200 aspirin instead of $100.
And you can’t shave it much. Doctors already complain medicare payments are too low. What do you do? Pay them half that much? Even fewer doctors will take medicare. Force doctors to accept medicare? Stop paying for medicare for the year when the pot is empty, say, the end of September? Pay people half the welfare they used to get? Their rent and food bills won’t be half what they were.
The devil is in the details. The problem is the USA spends $1.20 for each $1.00 it takes in. Cutting taxes supposedly with result in a bigger pie, but that has never materialized. But they provide certain services; this is what the services cost. Changing things, especially cold turkey, will only create massive job disruptions. People will lose jobs, businesses will close down, companies and people will go bankrupt, important tasks will not get done.
(OTOH - diatribe - every government in history has had a problem with money. Magna Carta was a result of too many taxes. Charles I lost his head over taxes; so did Louis XVI and his family. Henry VIII took over the monasteries and kicked out the pope not just over divorces, but because the church owned about 10% of the country and expropriating it was a good way to get money. This is nothing new…)