I totally understand what you are saying, but on the other hand: maybe a lot of US tech companies do unethical/bad things? Antitrust cases must be based on something, so it's not just tariff on tech company products, it's more like a fine for bad behaviour.
A study of the history of Antitrust would abuse of of that naive thinking.
The overall trend in anti-trust is that most of the issue is not that people have done demonstrably bad things: Rockefeller typically would over-pay for the distributors and wells that he purchased–and he was the only buyer. The issue was more that prior to the negotiation, he used often unconventional but legal tactics (like showing his books) to make clear that he could conduct a price war, and would ruin the company that he was offering to purchase. The price he did pay typically was low without that in mind, but every other potential buyer knew as much and stepped away.
The whole debate wasn’t focusing on measurable harm, but the ability to threaten, hence a focus on market share. Since, it has gone up, to catch less blatant, but not unjustified potential to harm the market: the key measure went from market share to Lerner index which measure the ability to raise your own price without loosing share. Apple typically has a small market share of smartphones worldwide, but seem to be able to raise their prices without loosing much sales; that allows them to corner supplies by over-bidding and retain feature exclusivity. It’s less morally obvious that this would hurt the market, but some executives at Samsung are probably adamant that this is a major concern, let alone smaller player.
There are still some hard evidence, but the bar has become surprisingly low: three cellphone providers in France were fined one Billion Euros (with a B) for price-fixing, based on the testimony of a taxi driver and a penciled-in and rubbered-off “Ok on Yalta” on someone’s notebook (and significant econometric proof that prices stopped going down). The discretionary ability of the Competition Authority becomes key, i.e. they ability to enforce a loosely defined norm of market preservation.
Current trend is closer to consider dynamic considerations, the ability of currently non-existent firms to enter the market: has Facebook’s ability to purchase Instagram and challenge Snap discouraged entrepreneurs? Facebook did nothing illegal buying one or offering feature that they users enjoyed on the other; however, that behaviour, couple with the ability to invest a lot of developers, can seem threatening and discourage entrepreneurs. Who do you ask if that was significant? Investors who said they wouldn’t invest on that basis? Young CS graduates?
Disclaimer: I was personally involved in most of the cases that I mention, either working for the company being looked into, or serving as an expert for regulators. I’m happy to provide context, but none of this should be considered testimony.