If Spain ditched Catalonia, it would probably go even further to the Right.
One difference between the Spanish conservatives and American conservatives is that the former supports strong central government. For centuries, separatist movements in the Basque country and in Catalonia were suppressed by both the monarchy and the Franco regime. It has been the Spanish socialist and communist parties that have supported independence for these provinces. In contrast, American conservative strongly support states rights and a weak federal government.