Territorial versus non-territorial taxation isn't such a simple issue. In a non-territorial system, it's very easy for a company to set up internal transfers to shift profits to whatever happens to be the lowest-tax jurisdiction.

Moreover, the U.S. system generally does not double-tax income that is already taxed elsewhere. A U.S. company that pays taxes on German income will receive a credit for those taxes paid against its U.S. liability: http://www.cbpp.org/research/the-fiscal-and-economic-risks-o....