Depending on what countries you’ve visited, if you’re a US citizen traveling abroad, you may not even know that most people need visas to visit different countries. That’s because the US has political agreements with lots of countries that have tourist-heavy economies, like Mexico, Iceland, Australia, and South Africa (to name just a few), acknowledging that travelers are welcome to freely visit without the governments strictly tracking their comings and goings. The number changes as visa requirements change, but it’s generally accepted that if you hold a US passport, you can travel to roughly 180 countries without a visa.
That still leaves a good handful of countries left to explore, however — and for those, US passport holders will need a visa.