Were it not for globally-focused big-tech companies, where would their stock markets be?
This is the key issue here. Presidentttt's gloomy prognistications focus on depressed conditions in, and depressing characteristics of, the US domestic market. But a company's share price is not really affected by the conditions and characteristics of the market in which it is headquartered, or where its shares are listed and traded. Share price is much more affected by the conditions and characteristics of the markets into which it sells its products and services. The more global, the more multinational, the more diversified the sales of a US-based or US-listed company are, the less the stock price is affected by domestic conditions in the US.
Apple, for example earns 35% of its revenues in the US. That's not trivial, but it leaves 65% of revenues earned in the rest of the world, including in the growing Middle Eastern and Asian markets to which Presidentttt posts.
And, interestingly, Samsung earns 39% of its revenues in the US, meaning that Samsung, a Korean company, is actually (slightly) more exposed to the US domestic market than Apple is. Which underlines the point that it's not a given that US-based companies, or US-listed companies, are more exposed to the US market than non-US companies. In so far as US domestic conditions do pose a threat to investment returns, it's not a threat you avoid by investing in non-US markets.
Something similar is true, incidentally, for all the world's major stock markets. The companies that make up the FTSE 100 index, for example, derive a surprisingly small share of their revenue in the UK (though I cannot offhand recall what that share is).