Local ingredients must be incredibly niche though? The amount of US beer that must use imported UK, German, Belgian hops? Even if grown locally, the varieties. at which point this is like comparing Shiraz & Syrah; South African Merlot with Australian. Except without a record of it making a difference at all itself - intuitively it should be subtler - hops are a component, 'grape juice' is the whole thing. The water used for ale (more analogous to grapes really) does have a documented effect. That's probably more homogenous than it used to be, and the big boys probably use distilled water and add whatever mineral components they want, but certainly that could be significant for US vs UK microbreweries, or certain intra country comparisons.