Japan (the country) doesn't do this. You still need a company to sponsor you and not every company can.

Because other countries are not Japan, and if, say, the US were to pursue a similar policy, they would receive over 200 million immigrant workers and near-zero employment among the native population in the first two years

Switzerland is the same. By far the best implemented immigration policies in whole Europe, if only Germany and France egos would step down a notch, acknowledge their mistakes and take an inspiration from clearly way more successful neighbour. They have 3x more immigration than next country and it just works, long term.

EU would flourish economically and there would be no room for ultra conservative right to gain any real foothold (which is 95% just failed immigration topic just like Brexit was).

Alas, we are where we are, they slowly backpedal but its too little too late, as usually. I blame Merkel for half of EU woes, she really was a horrible leader of otherwise very powerful nation made much weaker and less resilient due to her flawed policies and lack of grokking where world is heading to.

Btw she still acknowledges nothing and keeps thinking how great she was. Also a nuclear physicist who turned off all existing nuclear plants too early so Germany has to import massive amount of electricity from coal burning plants. You can't make it up.

Can you give more details here? I don't fully understand your post.