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Forgetting all other issues, I am assuming you are using a PHP redirect to accomplish this and that you have three sites: .co.nz, .co.au, and .com which you are using the geo targeting preference for US. Given that you have three sites, they will be indexed individually based on all the normal ways a site is indexed. So, links to site A will bring a googlebot. Sitemap of site B will bring same. Etc. If you are using some type of cross domain canonical or have any redirects of one site to the other for any reason, they will be followed across as well. All domains will be crawled independent of one another. So, you need to get links to each. Best,

Hi Ian, Thanks for this - that makes a lot of sense. Have been trying to contact the person who put them up but am yet to hear back (I'm forever hopeful though!). Unfortunately the links are pointing at the homepage, I have already decided to write off a few pages which are suffering from a set of different bad links. The new link building approach will definitely be good links - the website is for a business selling a quality product so there is no reason we can't build it up using normal marketing and avoid the spam! Thanks for your help.