Nationalizing in the traditional sense is not the solution, indeed, but rather hold the platform up to the letter of the constitution. This right now is not exactly possible given that "twitter is a private company", therefore arguably if one puts it in the hands of the government, you have the double-edged sword of potentially being abused by the government, and on the other hand the solution i forementioned on holding it accountable given that it would become public under the law. However, just like with any other gov. institution, being held accountable is more often than not up to the people through their civic initiative and probably not something that the government will do out of interest. So in this regard in US it could work given the nature of the constitution, whereas in other countries Twitter would just become a propaganda machine (isn't it one already?).