Brewing a campaign

[Warlord JK]

I've been coming up with ideas for making a campaign world, and thought a really cool one would be set where during a colonization time, comparable to the era before the Revolution, about 100-200 years before. There are all the old kingdoms across an ocean that have begun colonizing a "new world" across an ocean. A main problem with this idea was I want to keep it in late middle ages, no guns or very basic guns that aren't that good. Also didn't want the idea of South America. Any ideas how to make this work without going above early Renaissance technology level?