How do you pronounce "accommodation"?

In American English: /əˌkɑːməˈdeɪʃən/ (uh-kahm-uh-DAYSH-uhn). In British English: /əkˌɒmədˈeɪʃən/ (uhk-om-uhd-AYSH-uhn). In Canadian English: /əˌkɑːməˈdeɪʃən/ (uh-kahm-uh-DAYSH-uhn). In Australian English: /ɐkˌɒmədˈeɪʃən/ (ɐk-om-UHD-aysh).

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

Yes. In American English it's pronounced /əˌkɑːməˈdeɪʃən/ (uh-kahm-uh-DAYSH-uhn), while in British English it's /əkˌɒmədˈeɪʃən/ (uhk-om-uhd-AYSH-uhn).