Even though it may seem difficult for Western countries to join BRICS in the future, there may appear a time when countries will try to join. Especially when their own interests will be seriously affected by the long-term dominance of United States, it is not unusual for them to join BRICS to protect their national interests, where it is easier to expand trade. In the meantime, we know that there are some countries like France and Germany that have good relations with China. If they adopt such a policy in the future to protect their own interests, it will be realistic. Especially if BRICS works successfully in circulating their own currency against the dollar, then some countries in Europe will definitely try to free of the American regime.
That is very unlikely if not impossible, as they depend on the US not only economically but also militarily. The EU has been almost completely dependent on the US since World War II and to put it bluntly, the US has turned the EU into its lackey. Their relationship is no longer one of alliance and mutually beneficial cooperation in the literal sense. Therefore, the possibility of the EU leaving the US is unlikely.
Moreover, they also have their own calculations, what guarantees that Russia and China will welcome them with open arms? They would be in a dilemma if Russia and China did not accept them at that time, so they would consider carefully if they intended to move away from the US.
In my opinion, China and Russia are mentally prepared to accept the European Union countries, even if they do not say it openly and may not show it openly because it will increase US pressure, but they will be ready to accept it warmly. China and Russia will do this because it will break the US's exclusive control over the European Union. And Russia and China naturally see Europe as an ally of America. But if a European power comes to them, they will see it as a strategic victory and accept it because they think that if a European country joins BRICS, the US-led unity will be weakened, and this is an eternal truth.
However, some pressure may come on the European Union countries, especially the European countries that join BRICS. There will be various types of political pressure from the US, including tariffs, on them, but this pressure can be overcome. If Europe's economic power is added, the BRICS currency initiative will be stronger. Even if the economic and geopolitical balance is temporarily a bit unbalanced, BRICS will not be limited to the Global South but will be a transcontinental bloc. Then, even though the US' geopolitical game with BRICS continues externally, internally the US will be forced to accept the activities of BRICS.