This replaced a higher rate on US net income and global net income that lands in the US.

Let's walk down this rabbit hole:

So you want to tax corporate profits. Well, trouble is, it's easy to hide profits. For example, interest payments are subtracted from profits, which allows investors to lend money to corporations as loans, and the interest is only taxed by the recipient, but if you lend money to the corporation by purchasing equity, that is taxed twice. This asymmetric tax treatment incentivizes taking on debt and thus financial fragility and short-term thinking. OK, you say, let's treat interest and dividends the same. Then you have this issue with massive executive compensation, which is untaxed as it is treated as an expense. You'd like for that to not be tax-exempt as well. Thus you decide to tax value add -- that is revenue net of your cost of goods. That way, you catch cheaters, since if corp A reports something as a cost (payment to B), then B better record it as a revenue. B can't hide. Except now comes the foreign sector. What if B is a foreign company? There's the rub. One option is to say the foreign company also has to pay you taxes based on what it sells to A. This would effectively put an end to all the shell company shenanigans. To be fair, you can give credit for income paid to other jurisdictions so you don't end up double-taxing (like we do), but that's minor. So now you are happy with your system. You survey the landscape and what have you accomplished? A sales tax! This is just a value added tax, or VAT, which is another form of sales tax. But sales tax is regressive! And very unpopular. So there is this problem where Americans don't want a national sales tax of, say 20%, but they do want a corporate profit tax of, say 40%. And they are really angry when they see the effective corporate tax being so low, say 5%.

This reveals a cold truth, which is that corporations are effectively pass through entities for the human owners of the corporations. So why tax them twice? Well, because we have so many tax loopholes and such large trade deficits that 40% of our corporations are owned by foreigners that don't pay US taxes and 40% are owned by pension funds and tax-advantaged retirement accounts so that only 20% of US equities are subject to any tax at all. So this thrashing around about corporations reveals yet another uncomfortable truth, which is that our massive outsourcing has resulted in an erosion of the tax base just as much as it has destroyed middle class jobs.

This brings us back to a new variant of the old trilema, which is that you can't have free flow of capital (or equivalently, trade) across borders, a floating currency, and your own interest rate policy.

You can only have two of these. Except the tax version of this is that you can't have free flow of capital (that is trade), a floating currency, and your own corporate tax policy. The best you can do is a national sales tax for goods sold to your own citizens. If you try to tax corporations, you will run into the two-headed hydra that your corporations are owned by overseas investors and that your corporations have set up overseas businesses that sell them valuable inputs, so valuable that all the value is routed overseas.

So what happens is people create a tax policy that tries to also avoid tariffs on trade and foreign capital flows, and then they are shocked when corporations arbitrage that away.