x <- c("Total Assets in th USD", "Equity in mil EUR", "Number of Branches")
currencies <- c("USD", "EUR", "GBP")

regex <- paste0("\\b(",
                    paste(currencies, collapse = "|"),
                ")\\b")
# results in
# "\b(USD|EUR|GBP)\b"

regmatches(x, gregexpr(regex, x))