“She wants to nationlize Shell? Is this even possible?”
Theoretically government could “take” an oil company on the grounds of public good. Truman threatened to nationalize the railroads during the Korean War because of labor troubles.
However the 5th Amendment prohibits “taking” without just compensation. But if it got to the point where Maxine nationalizes oil companies, the constitution is meaningless anyway.
In the case of Shell. specifically, all they could take is that companies assets which are subject to the jurisdiction of the US (refineries, pipelines, terminals, production fields, etc.) Royal Dutch Shell would continue to operate, as a company all of their assets located internationally. They then could "fire" all US employee's w/o compensation, except as may be allowed under Dutch law.
Maxine Waters is an idiot who has not thought this through.