You must be misremembering the price disparity. A quick Google shows that Switzerland is home to "the most expensive big Mac in the world"[1] at 6.50CHF. Almost double the US's average of $3.99.
Nice! Thanks. Looks like my numbers were a bit off due to being out of date. To anyone who wants to know, currently the Swiss Big Mac is 35.4% more expensive than the US one.
[1]https://www.businessinsider.com/mcdonalds-big-mac-most-expen...