Yeah it’s a threat to the USD as the world reserve currency. Maybe not an imminent threat but as these countries gain strength & confidence, dealing with each other it definitely threatens the US. Trump does not like it, but BRICS is not going to go away, they are only going to have an increasing presence as time goes on.
Because of this threat to USD, it will make many countries to join BRICS to let Trump know that they can trade perfectly well among those countries without dollar. As long develop countries are showing interest to join BRICS like the way Indonesia country join recently, it will create more fear to US government because they think the unity of those countries will not stand but is making progress already, which there are some countries preparing to join BRICS soon, whether Trump like it or not, it will not going to affect those countries that have accepted BRICS, and they are ready to influence other countries to take a bold decision to embrace BRICS to make Trump know that many countries don't like his policy.
World War II is over, the system built by the US has declined, and the dollar as the axis of global trade has been slowly abandoned. Of course, this didn't happen suddenly; there must have been a reason why many countries are starting to reconsider their use of the dollar as a foreign exchange and medium of exchange.
Remember, the dollar's value was tied to oil in the previous agreement, which ended last year, resulting in the loss of the petrodollar's status. Saudi Arabia abandoned it, and now there is no meaningful underlying value for the dollar as a standard. Another reason is the US's double-standard political views. We have seen this for a long time. On the other hand, when it comes to military power, many countries have caught up and are able to match it militarily, so why should they submit to the US? The big question is why the BRICS countries are not aligned with the US.
Perhaps this also reflects disappointment with US leadership as the axis of the global economy and politics.