It is no wonder the foreign makes dominated the small capacity fields in 1969 when the only US opposition would have probably been the 4 cylinder 153 cu. in.(2.51 L) engine Chevy Nova which was too big a size for those classes and was a slug and most of those engines were used in US Postal trucks to deliver the mail !
So I guess being competitive in small bore class racing was not of importance to US auto manufacturers in 1969.