We compared Burger King in the UK and the US. We noticed a few key differences but still see why it's an international hit.
Briefly

While both the US and UK Burger Kings offered fairly similar portion sizes, our US reporter was definitely struck by the impressive quantity and spicy flavor of the chicken sandwich, highlighting a distinct American approach to fast food. This emphasizes the often-exaggerated American portion myth, yet also showcases how local preferences can shape menu items.
The dining experience in the UK Burger King reflected a more compact yet equally busy setting, appropriate for the urban Glasgow environment. The queues during lunchtime were significant, indicating a high volume of customers who prioritized speed and convenience, typical of fast-food dynamics in a city known for its bustling atmosphere.
Read at Business Insider
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