The 1658 attack on Copenhagen succeeds and Charles Gustav merges Denmark and Norway into his empire (this is a bit of a Hail Mary as many of the most important political actors at the time were explicitly against any power controlling both coasts of the Sound).
It’s a tad late to get a foot on the eastern seaboard of North America, but with dominion over the Baltic secured, Mega-Sweden can secure colonies in Africa, the Caribbean and in India.
Note that there was a New Sweden but it was conquered by New Netherland. Maybe have the POD slightly earlier and have the two countries avoid the conflict?