Why frame the question with regards to an upcoming event?
Periodically reviewing your investing policy statement and possibly changing your allocation is good practice, but I'd suggest the reasons to change your allocation are more about changing life goals, learning new things, changes to your family, maybe even significant tax law changes. But a US election? Not even close.
The most compelling argument for adding an international component, to me, is "Why would you want to hold Ford but not Toyota?". So, if you find that you want that in your portfolio, figure out how much and make the change. I personally went with approximately the US to international ratio that you find in Vanguard's Life Strategy Growth fund - my 3 fund portfolio is slightly cheaper and I get enjoyment out of annually re-balancing the account.