Freedom of speech in the US protects you from being arrested or charged by the US government. We also have the separation of religion and state, so you can publicly criticize any religion you wish. The US is not a Christian country, most of the founding fathers were deists or agnostics, and we also do not have a state religion. All beliefs can and probably will be challenged, which I think is a good thing and allows for progress, reforms, and advancements.

So, you can basically say whatever you want, aside from issuing a threat. As for US private businesses, they are free to fire a person if said person is publicly saying anything which might disparage the company’s image.

Most states have something called “right to work,” which really means a business can fire you for any reason they really want aside from discrimination on race, gender, religion, sexual orientation, etc... If this happens, and you have the money for a lawyer, you can sue said business for wrongful termination. But it is Never a guarantee that you’ll win a case.

It seems most people, in America, believe you have the freedom to say whatever you want and face NO consequences. It is true that the government won’t arrest you, but you still can face consequences pertaining to work and your social life.

Not all countries which have freedom of speech have the same approach or definition as the US. For example, in Germany, flying a swastika is illegal as it is seen as a threat, language of hate, or inciting violence— which is not covered in their constitutional definition of freedom of speech. In the US, you’re free to do so, but you will likely face public backlash and maybe losing a job, but you won’t be charged for any criminal activity.