The composer of this little bit of political speech seems to have been one of those free spirits who wasn't paying attention back in remedial English Composition. He may mean to express the view that "birtherism" is beneath the dignity or intelligence of right-thinking people. In that case, he ought to have used "than" instead of "then." On the other hand, he may have been attempting to communicate the view that America must first become better, and then we can get on with "birtherism." That thought would require at least a comma, but a colon (or even a dash!) would have worked.