Is there an easy global system to have a combined map? “name (name:en)” does not sound wise for the UK or US. But mapnik requires a single rendering rule and does not differentiate between geographic regions.
This might be preprocessed but sounds too for the main map on openstreetmap.org with it’s frequent updates.

I like more the approach of wikimedia to have renderings for the different target languages. This can take different fallback languages into account.

Stephan