As I recall, the US initially did not block arrivals from China, it blocked Chinese citizens. I read that 450,000 people traveled between the two countries after the "blockade".
On a somewhat related subject, anybody who can read the Chinese press (and social media- the new propaganda tool) will notice that in recent weeks the language changed and sounds like what you could read during the cultural revolution. It certainly has my Chinese friends over 50 years old somewhat worried as this language is all too familiar and brings back very bad memories. Foreigners and foreign countries are referred to as the enemy, foreigners in China are spies and Chinese who moved abroad are traitors, especially if they change passport. The expression traitor is used a lot these days and rather loosely.