There is no place on earth that has said "Not symptomatic? Wear a mask and carry on." and seen the curve flatten. As you say, a lot of asian countries _are_ enforcing mask usage. But none of them are just "carrying on".
IIRC China is enforcing a "1 person per household is allowed outside once every three days for supplies" policy in the most affected areas, has built multiple new hospitals, has implemented multiple cordon sanitaires, locked down millions, has _free_ testing, and is enforcing that testing.
South Korea, Singapore, and Taiwan were among the first to ban flights from China (and given where they are that's MUCH bigger than the US doing so, both politically, and in percentage of flights). They are testing people constantly before they're allowed out of or in to places. They are _enforcing_ quarantines of people with fevers, they are interrogating people that might have been exposed to the disease, and are quarantining based on that, even without symptoms. They have a _lot_ more people staying home than usual. They are accessing people's financial data in real time without warrants.
No one's saying masks make things worse. Given how many masks we have, there's an open question as to whether we should reserve them for medical care providers or not. What people are saying is that masks are not enough. And they're right.