None of those three countries have a highly-guarded technology advantage which the US is trying to catch up on.

China investing into US companies is completely separate from the IP issue. For all intents and purposes, once you've bought a company, you've bought its IP.

Buying a company is about the most legal way I can think of, for acquiring IP.

Again - how does allowing foreign ownership of companies in your country harm your country? You mention IP - but it's not your country's IP - it's a particular company's IP. If its owners want to sell it, why does it matter if they sell it to an American, or a Chinese investor?

> If its owners want to sell it, why does it matter if they sell it to an American, or a Chinese investor?

Because there are second order benefits to Americans of America being the world power. (E.g., Americans really don’t want to live in a world where you have to learn Chinese to succeed in the business world, as opposed to everyone else having to learn English.)

Those all can cause issues. Allowing mostly foreign companies to own the majority of a country's economic sector can turn out quite bad. In fact, it has happened in history with banana republics.