No, it doesn't always happen. Look to 2016 as an example. One of the talking points of Trump's campaign was that Clinton would lead the U.S. to war with Russia.

Anecdotally, after the election, I was talking with a Trump voter who mentioned that Trump prevented us from going to war with Russia. Which fucking surprised me, considering conservatives are so fucking hawkish, and I did not know that idea was tossed around in conservative circles as a talking point.

So no, many elections in the U.S. have been won by candidates that back isolationist policies (primarily WWI and WWII as an example). It's all inherently political and can take a very populist tone.