You moved the goalposts pretty substantially there. Your original statement was "You will not be able to ever run 100% renewable with today's technology" When this was proven false, you've narrowed the field to the US, as though the US is the only country that has this problem, and your only point appears to be that the US is bigger than some other places, and that parts of the US don't have much renewable generation yet.

Some forms of renewable energy provide spinning inertia themselves, and as I've pointed out above, spinning inertia can be provided from storage rather than generation. The technology already exists and is in use elsewhere.