I seriously doubt the US would have ever been 'eaten alive' by Europeans. Ignoring the problem of geography, and the difficulty of Empire, the English culture did wonders for a country smaller than Louisiana. Just the 13 colonies (given time) would have had an absolutely mammoth industrial core. Even without Manifest Destiny, most of the early US expansion into the midwest and Mississippi area was peaceful and done through trade and land purchases rather than land grabs. It was only with people like Jackson that it became demographic replacement, even of assimilated Indians.

Britain was actually the only real imperial threat the US ever faced; and they could never have defended Canada if we attacked with a competent army, or had even middling support from the Canadians. We lost in 1812 because we had shockingly incompetent officers, stiff Canadian resistance, massive internal turmoil, and hardly any industrial base. And we fought to a draw, effectively.

Reviewing "War Plan Red" shows the difficulty of a war with Britain at possibly the absolute peak of it's Empire, and at best, they'd still lose Canada eventually.

I seriously doubt the US would have ever been 'eaten alive' by Europeans. Ignoring the problem of geography, and the difficulty of Empire, the English culture did wonders for a country smaller than Louisiana. Just the 13 colonies (given time) would have had an absolutely mammoth industrial core. Even without Manifest Destiny, most of the early US expansion into the midwest and Mississippi area was peaceful and done through trade and land purchases rather than land grabs. It was only with people like Jackson that it became demographic replacement, even of assimilated Indians.