What Americans call censorship is not that. Anyone who is banned from a particular platform still has freedom of speech. They can say whatever they want to whoever they want without the fear of government prosecution. If Twitter bans someone, it doesn't mean that the banned person can't speak somewhere else. Everyone has a right to moderate their private property which includes digital space. Although banned from Twitter and some other platforms, Trump didn't lose his freedom of speech. He can say whatever he wants. It's just that he will need an alternative way to reach a big audience because major companies specializing in providing big audiences don't want to provide him their services.
One does not have to prosecuted by the government in order to have their speech censored, access to a public forum revoked, or have their livelihood and career threatened.
There are things you simply cannot say within our society due the fact that they are deemed subversive or improper. This arbitrary ability to ascribe these labels to speech and thereby limit its reach and punish those who speak it is the very abuse of power that is characterized as "censorship".
A government is one institution that concentrates power that can be a censor, but in modern times there are alternative organizational structures that are both powerful and global that can perform the act of "censorship".
Think of it in the language of physics. Regardless of the "Kinetic Energy" of censorship, the "Potential Energy" for censorship in is the US with concentrated power to decide who can say what and effectively remove people from public life and discourse is likely far greater than existed in a country like Croatia (which you believe to have had far greater "Kinetic Energy" than the US has).
The scant analysis provided under the "Assessment" stretches the words and context of the tweet to imbue it with the most uncharitable meaning possible.
This should be dismaying to non-political and political citizens alike, as well as supporters and non-supporters of this individual. I believe this because subduing your opposition with force (whether it be physical or social) is never an honorable way to triumph.