The entire Western world is currently in decline, not just in relative terms as a percentage of the global population or economy, but in real terms as functioning societies.
That being said, although all Western countries without exception are sinking under the weight of Third World mass immigration and in the process becoming a part of the Third World, they are not sinking equally fast. With the exception of France, Belgium and possibly the Netherlands and Sweden, the English-speaking world is leading the disintegration of the West, ideologically and demographically. The entire West is sick, but the Anglosphere is sicker than most. The English-speaking countries still have the most dynamic military traditions of the West, but that counts for little as long as they are used for promoting global Multiculturalism rather than for protecting the home country.
I cannot see that the Anglosphere has more freedom of speech than Continental European countries, either. The USA with its First Amendment does, which is great (we'll see what their new President does about that), but al-Canada is plain nuts and Britain is a Multicultural banana republic. Australia and New Zealand could be a part of Greater China by mid-century. Maybe they will be more prosperous than France will be as a part of Greater Algeria or the United States as a part of Greater Mexico, but by then they will be Asians, not Westerners.
I'm not sure why the Anglosphere is so bad. In the case of Britain, I strongly suspect it's partly caused by a Post-Imperial Stress Syndrome for a nation that once ruled much of the world and now cannot even rule its own suburbs. Empire was their identity. Much of the same can be said about the French. Indeed I suspect that one of their motivations for supporting the awful EU project is for them to resurrect some of their past imperial glory in another form.
Yet this cannot explain the actions of the United States, which is still the world's greatest power although that may not last forever. There is some form of universal proposition nation idea with roots dating back to the Enlightenment at work here. It's the concept that a country is not a nation based on a shared heritage, but an abstract entity which can be joined by absolutely anybody, a bit like an enlarged video club. If you claim that the United States is a "universal" nation and that Hamas-supporting Muslims, with which Westerners have absolutely nothing in common, can and should be imported to the USA, then you are a supporter of the concept of a proposition nation. This idea will eventually kill the United States as we once knew it.
While a secular theology of immigrationism certainly exists in the Anglosphere nations, a theology which teaches, quite falsely, that immigration is, and has always been, an integral part of their respective national characters, one cannot overlook the role that powerful transnational commercial interests have played in opening up the Anglosphere nations to massive Third World immigration. Continental European elites, in contrast, seem slightly more reluctant to throw their nations under the wheels of the "global economy" express.