That depends on your definition of ally, now does it not? I personally define an alliance as a pact made between two countries that are either friendly, or against a common enemy. Both apply to the US and Israel.
However, the term these days in this selfish and self serving world no doubt has changed, because everybody expects something back these days.
(Also, Israel returns the USA a base for Operations in the Middle East, albiet a unstable one, a nuclear power that basically will support any US action, and limited but still existing UN support.)