Even if you fix taxes on national level, you aren't going to catch multinationals. They keep moving just behind that inevitable race to the bottom.
Because in my country basically the governments hire law firms to write out legislation, and then those same law firms sell these types of services to circumvent the laws they draft.
So the feeling I get it's not much a taxes problem, but the public institutions are managed by lawyers, and are optimized by lawyers that leave enough margin so they can thrive.
And why should they ?? To quote Steve Eisman "incentives trump ethics every single time".
Here's a tax strategy that will greatly simplify all government efforts: any corporation with a market cap of 100bn+ is obliged to sign a privately negotiated deal with the gov to agree on a annual tax rate for the next X years. The minimum is set at 20% with no exceptions and can go up to 50% depending on the estimated negative social impact of the corporation. There are no write offs, no loopholes. Every year the tax bottomline is checked and enforced.
There is also a tax distribution enforced so that only a few can get the 20% one at any time. The goal of this to force a "bidding war" between them to get the lowest tax and the only way to do that is to reduce their negative impact to a bear minimum or stop existing altogether. Incentives.
Once that is set in place work on reducing the tax code complexity for everyone and everything below 100bn. Currently most if not all tax regimes try to shoehorn all entities under the sun under similar rules and then provide various kinds of tax write offs that create incentives to dodge tax and provides the biggest players with a massive advantage as they can hire specialists to focus on every single possible loophole to avoid paying anything.
The problem is they aren't cheating. They are hiring a lot of lawyers to find every single LEGAL mechanism in the book to allow them to pay no taxes.
I'm not saying I agree with it. But the problem here isn't with Amazon it's with the US tax code, which has been molded over decades of politicians and lobbyists to allow for this.
To fix the system you need to fix the tax code.