Final answer:
The American's ability to think on his feet can be inferred by comparing the quick ad-libbing of politicians during speeches to similar situations where the American might need to adapt or respond swiftly.
Step-by-step explanation:
The evidence that supports the idea that the American is able to quickly think on his feet is not explicitly provided in the text snippets, but we can infer from the provided context. For example, when politicians craft their speeches, they engage in 'thinking slow' but when they ad-lib during the delivery, they must think fast. Similar to how they must respond to unexpected questions or situations with quick wit and agility, the American might demonstrate a similar capacity for quick thinking in his or her actions, such as quickly adapting to a change in a discussion or swiftly coming up with a solution to an unforeseen problem during 'The Dinner Party'.