I don't know about that, because long-range transmission significantly reduces the intermittency, even for the same longitude. It's not just about smoothing out the curve of solar production, demand patterns (due to weather, industry, behavior) will also have variations from place-to-place and these allow opportunities for power export.
Some places will have more dispatchable and expensive power plants than others, which also creates an export opportunity so that power is exported so that one country can burn less fuel. However, I admit this argument is slightly undercut by the question "can't we just build solar panels in the country with dispatchable dirty power?" True, but there's also a connection to wind power which is super local and random.