What if the result of breaking up US monopolies is their replacement by non-US monopolies?

How is that better?

I'd think very, very hard about crippling US companies in a global marketplace. So far, I don't even see any discussion about it.

If foreign monopolies take over then the US government should ban or regulate them in the same way that domestic companies are regulated. Foreign monopolies may (or may not) dominate global markets, but I think that concern should be lower priority than the health of our own markets and the well-being of our citizens.

So are we going on to put up a great firewall preventing you from using Tencent?

Seems very unlikely.

Considering how many of those big tech companies rely on pushing ads, does it really matter whether they’re based in the US or not? Either way, they’re revenue is from selling out their users.

For tax reasons , probably yes.