Theoretically they don’t necessarily have to be zionists, they could just be terminally lib-brained and think that adopting anti-zionism will hurt their electoral strategy or something.
Though sadly it is the case that there exists many liberal zionists who mistakenly believe that there could exist a progressive Israel which isn’t based on ethnic cleansing and genocide, and they don’t want to go full anti-Israel because they support this imaginary unattainable state.
European century of humiliation LET’S GOOO 
What groups inside the vassals would be plotting such an opposition? The US and Europe are not separate things, they are just parts of the world capitalist empire. The capitalists freely move their capital and their residency between the countries of the empire, and the European politicians likewise are guaranteed cushy gigs in international organizations if they don’t rock the boat. These people have nothing to gain from loyalty to their country and trying to oppose the US, and everything to gain from just keep selling out their countries like they have been doing.
YAWN this thing is still going on ??
BORING
Dios mio! A liberal!