What is the ERC (European Research Council)? Find more information here:

-ERC website
-Euresearch: the Swiss guide to European research & innovation

Q: Research topics in humanities are often quite regional (e.g., a research topic in Swiss history). Do such projects have a chance for an ERC Grant?

If they generate new knowledge beyond the state of the art, they have a chance. However, it must be shown in the proposal that there is a general gain of knowledge with more than just regional aspects.
Have a look at the ERC grant winners and their projects in the SH domain by checking the funded projects on the ERC website (you can refine your search with keywords in the search function).
Generally, there is no reason to believe that researchers from the Humanities have less chance than researchers from other domains. In EU average, the success rate is more or less the same in all domains. However, it is true that Switzerland has disappointingly few ERC grants in the Humanities. Euresearch is undertaking several measures in order to rise awareness and support researchers from the Humanities. If you are interested, contact your Swiss National Contact Person.