When I try too see it from the pilgrims perspective I think: they could have evangelized the natives, evangelization leads to contact and eventual mixing. But apparently none of this happened.
When I try to see it from the spanish and portuguese perspective: evangelization did lead to mixing BUT then the caste system was created, probably to dissuade mixing, however people kept on mixing, despite their children having a lesser legal status, and I just don't get it.
This has been answered here a few times before. Essentially the English sent families to colonize the new lands, whereas the Spanish sent men to work there for a while, make their fortune, then return to Spain.
/u/drylaw had a very nice write-up about early Latin American immigration https://www.reddit.com/r/AskHistorians/comments/9hpan7/when_did_spanish_and_portuguese_women_begin/e6e94x3/
While Mamertine is correct, it should be noted that sometimes North American colonists were driven to go, or simply willing to go, native. Most notorious for the Pilgrims and the neighboring Boston Bay Puritans was Thomas Morton. He had very tolerant Christian beliefs that conflicted with the Puritans', and an admiration for the Algonquins and their culture. He set up a trading post near Plymouth, called Merry Mount, and was a problem for the Puritans on both sides of the Atlantic, until his political influence in England waned with the Puritan Revolution, and they were able to jail him.