Those links show that out of all Americans who vote in presidential elections, well above 90% vote for either a Democrat or a Republican. However, that does not mean that well above 90% of Americans are either Democrats or Republicans.
PS Americans also overwhelmingly vote either Democrat or Republican in non-presidential elections, even down to the city council level.
Americans overwhelmingly abstain rather than voting for any of the offered candidates, Democrat, Republican, or independent or minor party, in non-Presidential elections. 2018 had the highest midterm turnout since the before the Reagan era, and it reached the whole way up to 49%.