My recommendation would be to focus on ASO, through localized ASO you will be able to capitalize not only on the Euorpean demand, while also tapping into the US market.

Another well known strategy I've successfully employed in my app portfolio for premium paid apps is to rotate them from paid to free, delivering a massive amplification in downloads and then rotating back into paid. If you have built-in in-app purchases you can also explore the freemium route in more competitive markets.

I've built an app empire of 200+ apps so have some solid frameworks for exploiting the organic traffic available in the app store, which can be complimented by paid activity.

I'd be happy to jump on a call to discuss some activity you could get running immediately to boost your downloads.

Cheers,
Mike