We know this because the US just vetoed Palestine's bid to become a full UN member state, after lobbying other countries to vote against the resolution?—?despite continually saying it supports the foundation of a Palestinian state. Washington's words say one thing, but its actions say the opposite.

This is because if the US admitted its actual position, it would greatly damage its reputation on the world stage. What the US actually wants is the same thing the Israelis want: for the Palestinians to go away, or lie down and submit completely, or otherwise stop being an inconvenience until they're a forgotten footnote in the dustbin of history. But the US can't come right out and say this, so it pretends to support a two-state solution that Israel has spent years doing everything it can to ensure never happens. It's a completely fictional resolution to a very real problem, but the alternative to supporting it is to admit you support continued apartheid, oppression, ethnic cleansing and genocide.