First, how possible is it for a country like the US to accept a decentralised asset as a reserve?
not 'as a reserve'.. but instead invest x% of the reserve in other assets.. US gov already invests in other assets they dont control, such as other nations bonds, other nations natural resources
You are right about the US government investing in other nations' bonds and even more, but we should not ignore the fact that these are centralised systems. They have the political power and economic rights for the countries to fulfil their obligations to them. This may not be a direct control but still the traditional way. Can we say the same about Bitcoin? The US will continue to tread carefully.
Again, the x% reserve you mentioned for another asset, is it not the same as depleting their reserve to buy another asset they will keep? Is that not reserving through another asset (Bitcoin)?
I am pretty sure that investing in other nations is also a way of diversification as well, if your nation does badly, while others do fine, then you get to make money from the other ones who are doing fine and you are not going that bad.
Why do you think most nations have dollars in their reserves? Because they trust that USA will do fine, at worst case, whenever they do too badly, they just go into a war, get resources of another poor nation, and make a lot of profit form it. Look at Iraq, they got back form there a lot richer, not in military sense, tax payers paid a lot, but the private companies made a killing there, literally, and then the growth of the nation was much bigger for a long time. If we look at El Salvador, we can see that they do have a reserve and they are doing pretty alright for their situation and I believe we can make a profit based on whatever we can see from there. USA could do the same, for a lot more money and could be richer.
What are you even saying? This is not related to this discussion in any way, I mean to my post you directly replied to. No one is saying the US is not investing in other countries' assets, just like @franky1 pointed to the country's investment in other countries' bonds, it is part of the QE (Quantitative Easing), a monetary policy to stimulate the economy. Diversification or not, are they not doing it in the traditional way they know? Is any of those investments in blockchain/decentralised systems?