Complex sentence: Trudeau then faced unexpected challenges in his strongest region of Quebec, starting with increasingly bitter relations with Quebec Liberal premier Robert Bourassa as the latter took populist stands against Trudeau on the constitution, French language laws, and the language of air traffic control in Quebec.
Split into simpler sentences: Trudeau then faced unexpected challenges in his strongest region of Quebec, including a personal feud with Quebec Liberal premier Robert Bourassa. Bourassa started to take populist stands against Trudeau on the constitution, French language laws, and the language of air traffic control in Quebec.