I heard some Christians saying that America was founded on Judeo-Christian morals?

But didn't the first Christians that came to America steal the country from the (pagan) native Americans, is stealing a Christian virtue? And wasn't the country found on Native American principles before it became Christian, is it not time for change again? Maybe secularism isn't so bad, I mean it is working for Sweden and most other countries in Western Europe, so why not in the USA?