It's not contradictory at all. I'm repeating other answers, but I will add some context:

Ethno states are not necessarily against the existence of other ethno states. What better for a white american than a place just for the others?

In fact, nazi germany allowed some german Jews to immigrate to the british palestine with some of their assets (vs just fleeing): https://en.wikipedia.org/wiki/Haavara_Agreement

(I should mention that Hitler didn't support the state, so it's not a 1-to-1, and libyan Jews were sent back to europe to be killed by the Italians )

A group of white americans established the American Colonization Society to encourage Black americans to resettle in what would become Liberia. Lincoln also sent freed Black americans to Haiti.

The other reason is the christian belief that the Rapture (and return of christ) cannot occur until the Jewish people return to isreal. It's called christian zionism. Even as a child in the 90s in a roman catholic church we hear about how the jewish people were favored by god and we must support israel. I think the context of that was fundraising for settlement orgs.

The White Christian Nationalists are hoping to start the end times.

To add to other answers, the existence of Israel is an important checkmark in the Christian end-of-days mythology.

May I suggest the belief system of KeepThemOverThereism?

Nationalism is the belief that the world should consist of ethnically-homogeneous nation-states—so it’s perfectly consistent for nationalists in one country to support other nationalist states outside their own.

Besides the other answers here; Israel and USA also share a colonialist history.

Both are nations established on other peoples land, after genociding said people.

Manifest Destiny is the belief that you are not just entitled to steal the land of "inferior people", but it is going to happen no matter what. Doesn't this sound a lot like zionism?

Israel is the only country, except for the US, that is build on racial chauvanism, genocide and expansionism.

You are asking for rational thought from irrational people.

According to the story, the return of Christ and the Rapture depends on Israel.
I don't know the details. But that's how they can dislike Jews, while supporting Israel.

American Christians have always had a complex relationship with Judaism. On the one hand the American sentiment toward racial, ethnic, and religious purity is deeply ingrained and an important control mechanism for the corporate aristocracy. On the other hand it's very clear that textually they don't get heaven if Jews don't control Jeruselem and rebuild the Jewish temple... again. How they square this tension is individual. Most don't know or care that it's a self-contradictory position. Of those who know, most do the "God works in mysterious ways" thing, and there's also a menagerie of different smaller attempts to rationalize it, only a few of which include actually discarding racism. Ultimately it almost always boils down to a contradiction though, so yes, fundamentally, their answer is hypocrisy, or just ignoring the conflict altogether.

It's not that many people, population-wise.

It's that they are very vocal and they spend a lot of money lobbying and on propaganda.

And they are very much aligned in their worldviews and their goals in their own nations. Same reason these blocs often are aligned with the Putin's Russian and glad to take money from Russian sources.

The doublethink is part of it but American Christians are famously uneducated in their own religion and they feel a debt to what they see as Christianity's originator and ally against the heretical Islamists. Mix all that up with a media industry disproportionately ran by Zionists and you've got the current conundrum.

"We'll deal with the jews again when the arabs aren't an effective scapegoat anymore"

Is my wild stab at their reasoning.