Well, if you want jerusalem to be the English national anthem then you can vote for it here:

http://petitions.pm.gov.uk/Anthems/

And there is actually an organisation/ website campaigning for an english anthem. You can find it here:

http://anthem4england.co.uk/
http://anthem4england.co.uk/modules/wordpress/

And for debates about the english national anthem and englisness in general see here:

http://www.thecep.org.uk/news/

hope it helps....