I don't think any conservative, lease of all myself demanded unwavering obedience to anyone--let along a US president.  In fact I don't know what George Bush has to do with this discussion.

When Pope Francis is talking about immigration policy, government policy on the poor, etc, he is free to state his opinion.  But those things are prudential judgments.  Catholics can be at odds with the pope on matters of prudential judgments.  There is not one right way to help the poor.  Pope Francis has his ideas, and conservatives have their own ideas.  Unlike Pope Francis, conservatives do not think an entitlement based society helps the poor-in fact we believe it enables poverty--and is thus more harmful.  

When JPII and Benedict VI talk about moral teachings: abortion, contraception, divorce and remarriage, those things are not prudential judgments.  Catholics are not free to be at odds with the hierarchy on these issues.  

That is what makes this different.