"We periodically need replacements for our magical energy making machines" is a problem, but it is orders of magnitude less severe than "we will run out of fuel for our furnaces tomorrow."

That said, "running out" of oil isn't necessarily a real problem for the US, as we're net exporters of oil. The oil we export isn't the same kind as the oil we refine, but we could build refineries to refine our own oil and achieve "independence" that way. It'd just be less profitable.