Don't think of the US as having foreign exchange reserves. Other countries have foreign exchange reserves, basically all in US dollar-denominated instruments.
This is misleading if not outright wrong [1][2]. The United States absolutely has foreign reserves, and nearly all countries hold foreign reserves that aren’t solely “basically all in US denominated instruments”. Nor can one just wish away the fact that the USD isn’t the only strong currency in the world, nor the only asset foreign countries hold; diversification doesn’t only apply to individuals.
