Are there cross-cultural studies of this effect? If you are wrong, trustworthy fonts will have the same set of properties in cultures with similar alphabets. Pair of cultures which rate trustworthiness of fonts differently despite sharing the same language and alphabet could prove you.

I believe there is too much homogeneity among cultures using the same fonts (i.e. latin alphabet) that there isn't going to be such a case.

For example, hand-writing-like fonts are used in comics both in US style, european and south american stuff; newspapers and books have been printed with serif fonts since about forever; international brands look the same; MS Office/windows has provide everyone with the same fonts for decades.