The complexity of this agreement and its execution are incredible. Not only getting alignment from 130 members, but a system by which companies report their revenue _and the cost of the revenue_ for every country! Future tax avoidance schemes will most likely try to "divert" their costs towards high-revenue countries like the US. After all, what is the profit margin of an iPhone sold in Romania?
For some context, corporate tax makes up around 7% of the US's federal revenue. While this legislation is important, it's a fraction of the overall revenue pie.
A lot. Changes in policy cut the effective corporate tax rate down from ~40% around 1950 to where it is today. Lyn Alden covered this in an excellent post: https://www.lynalden.com/tax-shift/.
For some context, corporate tax makes up around 7% of the US's federal revenue. While this legislation is important, it's a fraction of the overall revenue pie.