Root domain with multiple subdomains question

I have an ecomm site with a root domain and two sub domains based on country, i am going to start an aggressive SEO strategy for them but im confused as to what domain i should be posting all of the content on and ultimately promoting for backlinks.

I know the obvious answer is the root domain but i heard conflicting suggestions because we have auto IP geo detect on to route users from the root domain to their country subdomain and i heard this would then not show the root domain in that users google SERP.

The country we are most concerned about ranking in is the USA but unfortunately right now that domain is a sub domain.

Any ideas and suggestions welcome.

I am little confused but each domain will work as separate site and you need to do for each one separately.

Nut-Nights said:

I am little confused but each domain will work as separate site and you need to do for each one separately.

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Maybe my question should be, how does google treat redirects? For example if I try and rank my root domain, and a user is in another country will my root domain show up in SERP and they will be directed to their countrys page?

subdomains are treated like seperate websites. Big franchises like roto rooter will usually use subfolders. You may want to use subfolders if u want to power up ur domain .. www.abc.com/italy