Global currency integration is happening in two main ways: countries are either adopting the US dollar or creating a single currency zone. This is driven by the fact that smaller countries struggle to compete with larger ones in the global economy. The reason for this is that governments can't simultaneously control their own monetary policy, keep exchange rates stable, and allow free movement of capital. Dollarization means giving up control over your own currency, while a single currency zone works best when economies are similar. However, both approaches face challenges.