Is an American AAS degree the equivalent of a British Foundation degree?

It sounds somewhat similar if a US AAS degree is indeed equivalent to the first two years of a four year bachelor's degree. A UK foundation degree is equivalent to the first two years of a three year bachelor's and can be converted to a full degree by completion of a top up year. It is much like an HND (Higher National Diploma).

That would make an AAS a lower level qualification, more equivalent to an HNC (Higher National Certificate). (The first year of a US degree is below the level of the first year of a UK degree.)

The other answer that says a UK foundation degree prepares you to start a bachelor's degree maybe be thinking of a foundation diploma in art and design or a foundation year run by universities (such as to accommodate international students with less rigorous high school backgrounds OE students who haven't studied prerequisite A-levels.) These are completely different to the foundation degree FdA.

Not really. An associate's degree from a US community college is the equivalent of the first 2 years of a 4-year bachelor's degree. UK's Foundation is preparation to start a bachelor's degree from the start, & does not include university-level coursework which applies toward the bachelor's degree.

Hmmm