US multinationals invest and generate significant income abroad. In this report, we expand the International Investment and Capital Model to model average effective and marginal tax rates on income earned from foreign investment by US multinationals. We evaluate the impact of the Tax Cuts and Jobs Act on the tax burden of foreign investments. We model essential elements of the US taxation of foreign income, such as deferral of foreign earnings and the global intangible low-tax income minimum tax regime, before and after the Tax Cuts and Jobs Act. Given the prevalence of income shifting by US corporations, we incorporate profit-shifting behavior and show its impact on average effective and marginal tax rates. We show whether the Tax Cuts and Jobs Act increased or reduced effective average tax rates depends on three crucial factors: the amount of profit generated by the new investment that is shifted to a tax haven, the deferral cost until 2017 of keeping income abroad to avoid paying US taxes upon repatriation, and the treatment of excess foreign tax credits. Firms with a higher cost of deferral before the Tax Cuts and Jobs Act benefit more from the tax reform and the shift toward a territorial system. Firms that shift profit heavily are negatively impacted by the Tax Cuts and Jobs Act because of the global intangible low-tax income minimum tax.