Multple Campaigns running together

Hi, I wonder if anyone can shed some light on the impact of running multple campaigns at the same time for the same countries with the same keywords! Also how languages and countries affect the campaigns

We have a North America Campaign which runs 24x7 with North American countries selected but with multple lanagues selected for the campaign. What impact do the selected languages have?

At the same time, we also an International Campaign, which currently has only Northe America, UK and Ire selected and only English Selected for Language. As our admanager is in Pacific time, this campaign is set to run 12:00am through 10:00PST, which is 8:00am through 6:00pm UK. This campaign seems to not be yeilding good impressions or conversion and it has come to me, that the two campaigns might be working against each other because North America is selected in both Campaigns. Culd this be the case? We are seeing some conversion for UK, but from the NA campaign, yet our Int Campaign is yeilding some impressions but poor conversion. How does google decide which campaign to use?

How does selction of Country and Language impact the campaigns? Is country related to which google portal the ads will appear in? IE: UK, is for google.co.uk Are all campaigns displayed on google.com regardless, or does North America have to be selected?

Sorry for the long blog, this has been doing my head in for days!

Sean