The circumstances were much, much different. The British colonized mostly empty land.
When Spain started colonialism, transoceanic travel was in its early stages and was a deadly, once-in-a-lifetime thing, never to return from it. It wasn't rare that half of the people who attempted the trip would die in it.
For this reason, most people who would embark on such an adventure would mostly only be men. So they couldn't bring their own women until much later.
That's one reason the continent is a mestizo hellscape.
The second reason is that most of North America was mostly unpopulated, with just a few nomadic & semi-nomadic tribes here and there, whereas Central & South America were highly populated, with entire civilizations of their own.
So no matter how many Europeans would try to cross the ocean, their genetics would be a drop in the ocean compared to the MILLIONS that already lived there.
Still, it turns out that most (>90%) modern day "native" people have the male Y chromosome of European origin, yet 90% of their overall genetics were still native. Really says a lot about what happened in the early years.