The accusation came at a NATO summit after Trump had questioned ongoing US military presence in Germany. He based his claim on Germany’s import of Russian oil and natural gas. Most of Europe has long purchased Russian fossil fuels, particularly natural gas, given the expense of having it shipped overseas. The US was also a net importer of oil and had until recently had also been a net importer of natural gas.

Politico EU – Trump Tips Into Germany at NATO Chief Breakfast
US Energy Information Administration – Oil Imports and Exports
US Energy Information Administration – United States has been a net exporter of natural gas for more than 12 consecutive months