The US gets a lot of flak for its high debt dollar amount, but realistically the more important metric is debt to GDP ratio, which is a decent indicator of a country's ability to sustain its debt. The US is somewhere around 105% currently, right around the same level as Belgium. For comparison, Japan is almost 250% - basically leveraged to its gills - but tends not to get the same level of bad press. The US should certainly be trying to lower that ratio, but we're still pretty far from Greece-level of crisis.

In actuality, if the US's reserve currency status went away it might be a good thing for our debt since the dollar value on forex would drop and exports would increase. It would also be easier for the US to inflate its way out of crisis in comparison to today.