You expect 300 million people to get a KN95 mask? And where, pray tell, are they to get them?
And again, where do you expect 300 million people to get surgical masks from?
And keep in mind, this doesn't mean that 300,000,000 masks are needed. It means many, many, many times that much.
These are not durable, long-term-use products; these are disposable products, meant to be used for a relatively short time, then thrown away. I don't know how long it is reasonable to use one, before discarding it, but I would have to say that to wear one for an eight-hour work shift would be excessive. I find that they get yucky/gross within about an hour or so, and after wearing one for that long, I have to discard it, and put on a fresh one. Anyone who is wearing one of these any longer than that is almost certainly creating far greater sanitation hazards* than it can be anywhere near to plausibly be claimed is being avoided by the use of these masks.
So, if I were to wear these type of masks when I am out in public, around other people, I would need a minimum of six to eight every day, probably more like ten or twelve. Now, multiply
THAT by your 300,000,000.
* And, of course, I do not think it has yet been addressed in this thread, the sanitary hazard created by improper disposal of all these masks.