It could be a matter of having the whole process happen in the US. In the sense that those 2 companies are the only one that have sufficient domestic supply chain for production, while all other companies need to rely on import.
But if that's the case then you could get source materials from one of these companies and give them to another manufacturer who normally ships from overseas, right? Like I'm saying in that case the issue seems to be lack of sufficient source materials in the US, not US manufacturing capability?
But in any case, the supply chains of companies that use overseas materials have been disrupted. With effort, they could probably switch to using materials from a domestic manufacturer, but those manufacturers may not have the capacity to satisfy the increased demand. Per the OP, it seems like the limiting factor in production is melt-blown fabric.
