How do you pronounce "expectation"?

In American English: /ˌɛkspɛkˈteɪʃən/ (ehksp-ehk-TAYSH-uhn). In British English: /ˌɛkspɛktˈeɪʃən/ (ehksp-ehkt-AYSH-uhn). In Canadian English: /ˌɛkspɛkˈteɪʃən/ (ehksp-ehk-TAYSH-uhn). In Australian English: /ɛkspɪktˈeɪʃən/ (ehksp-ikt-AYSH-uhn).

Is "expectation" pronounced differently in American and British English?

Yes. In American English it's pronounced /ˌɛkspɛkˈteɪʃən/ (ehksp-ehk-TAYSH-uhn), while in British English it's /ˌɛkspɛktˈeɪʃən/ (ehksp-ehkt-AYSH-uhn).