src/Money.php
public function format(bool $displayCountryForUS = false): string
    {
        $formatter = new NumberFormatter('en', NumberFormatter::CURRENCY);

        if ($displayCountryForUS && $this->currency === 'USD') {
            if ($this->amount >= 0) {
                return 'US' . $formatter->formatCurrency($this->amount, $this->currency);
            }
            return '-US' . $formatter->formatCurrency(-$this->amount, $this->currency);
        }
        return $formatter->formatCurrency($this->amount, $this->currency);
    }
public function format(bool $displayCountryForUS = false): string
    {
        $formatter = new NumberFormatter('en', NumberFormatter::CURRENCY);

        if ($displayCountryForUS && $this->currency === 'USD') {
            if ($this->amount >= 0) {
                return 'US' . $formatter->formatCurrency($this->amount, $this->currency);
            }
            return '-US' . $formatter->formatCurrency(-$this->amount, $this->currency);
        }
        return $formatter->formatCurrency($this->amount, $this->currency);
    }
Returns a rounded string with the currency symbol

@param bool $displayCountryForUS Set to true if you would like 'US$' instead of just '$'
@return string